The estimated time of evacuation t p from work premises and buildings is determined as the total time of movement of the human flow on separate sections of the route. Calculation of the required evacuation time

MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION FEDERAL AGENCY FOR EDUCATION State educational institution higher professional education "Orenburg State University"

Department of Life Safety

CALCULATION OF EVACUATION TIME

Introduction

1 Calculation of the permissible duration of evacuation in case of fire

2 Calculation of the evacuation time

3 Calculation example

Appendix A. Table AL - Production Categories

Appendix B. Table B.1 - Degree of fire resistance for various buildings

Appendix B. Table B.1 - Average rate of burnup and heat combustion of substances and materials

Appendix D. Table D.1 - Linear velocity of flame propagation on the surface of materials

Appendix E. Table E. 1 - Delay time for the start of evacuation

Appendix E. Table EL - Human projection area. Table E.2 - Dependence of speed and intensity of traffic on the density of human traffic

Introduction

One of the main ways to protect against damaging factors Emergency situation is the timely evacuation and dispersal of personnel of facilities and the population from hazardous areas and disaster zones.

Evacuation is a set of measures for the organized withdrawal or removal of personnel from facilities from emergency zones or emergency probabilities, as well as life support for those evacuated in the area of ​​deployment.

When designing buildings and structures, one of the tasks is to create the most favorable conditions for human movement in a possible emergency and to ensure its safety. Forced movement is associated with the need to leave a room or building due to a hazard (fire, accident, etc.). Professor V.M. Predtechensky for the first time considered the foundations of the theory of human movement as an important functional process inherent in buildings for various purposes.

Practice shows that forced movement has its own specific features that must be taken into account to preserve the health and life of people. It is estimated that about 11,000 people die in fires in the United States every year. The largest catastrophes with human casualties have recently taken place in the United States. Statistics show that the largest number of victims is due to fires in buildings with mass stay of people. The death toll in some fires in theaters, department stores and other public buildings has reached several hundred.

The main feature of forced evacuation is that in the event of a fire, already at its very initial stage, a person is in danger as a result of the fact that the fire is accompanied by the release of heat, products of complete and incomplete combustion, toxic substances, collapse of structures, which in one way or another threatens health or even human life. Therefore, when designing buildings, measures are taken so that the evacuation process could be completed at the required time.

The next feature is that the process of movement of people, due to the danger threatening them, instinctively begins simultaneously in one direction in the direction of the exits, with a certain manifestation of physical efforts in some of the evacuees. This leads to the fact that the passages are quickly filled with people at a certain density of human flows. With an increase in the density of streams, the speed of movement decreases, which creates a quite definite rhythm and objectivity of the movement process. If, during normal movement, the evacuation process is arbitrary (a person is free to move at any speed and in any direction), then with a forced evacuation this becomes impossible.

An indicator of the effectiveness of the forced evacuation process is the time during which people can, if necessary, leave individual premises and the building as a whole.

The safety of forced evacuation is achieved if the duration of the evacuation of people from individual rooms or buildings as a whole will be less than the duration of the fire, after which there are exposures that are dangerous to humans.

The short duration of the evacuation process is achieved by constructive, planning and organizational solutions, which are standardized by the corresponding SNiPs.

Due to the fact that during a forced evacuation, not every door, staircase or opening can provide a short-term and safe evacuation(a dead-end corridor, a door to an adjacent room without an exit, a window opening, etc.), design standards stipulate the concepts of "emergency exit" and "escape route".

According to the norms (SNiP P-A. 5–62, p. 4.1) emergency exits doorways are considered if they lead from the premises directly to the outside; into the staircase with access to the outside directly or through the lobby; into a passage or corridor with direct access to the outside or into a staircase; v adjacent premises on the same floor, with a fire resistance of at least III degree, not containing industries related to fire hazard to categories A, B and C, and having a direct exit to the outside or into the staircase (see Appendix A).

All openings, including doorways, that do not have the above signs are not considered evacuation and are not taken into account.

TO evacuation routes include those that lead to an emergency exit and ensure safe movement for a certain time. The most common escape routes are walkways, corridors, foyers, and stairs. Communication routes associated with a mechanical drive (elevators, escalators) do not belong to escape routes, since any mechanical drive is associated with energy sources that can fail in a fire or accident.

Emergency exits are those that are not used during normal traffic, but can be used if necessary during a forced evacuation. It has been established that people usually use entrances during forced evacuation, which they used during normal movement. Therefore, in premises with a mass presence of people, emergency exits are not taken into account for evacuation.

The main parameters characterizing the process of evacuation from buildings and structures are:

The density of the flow of people (D);

The speed of movement of the human stream (v);

Path capacity (Q);

Traffic intensity (q) ;

Length evacuation routes, both horizontal and inclined;

Width of evacuation routes .

The density of human flows. The density of human flows can be measured in various units. So, for example, to determine the length of a person's stride and the speed of his movement, it is convenient to know medium length section of the evacuation route per person. The stride length of a person is taken equal to the length of the section of the path per person, minus the length of the foot (Figure 1).

Figure 1 - Scheme for determining the step length and linear density

In industrial buildings or premises with low occupancy, the density can be more than 1 m3 / person. The density, measured by the length of the path per person, is usually called linear and is measured in m / person. Let us denote the linear density by D.

A more visual unit for measuring the density of human flows is the density per unit area of ​​the evacuation route and expressed in people / m2. This density is called absolute and is obtained by dividing the number of people by the area of ​​the evacuation route they occupy and is denoted Dr. Using this unit of measurement, it is convenient to define throughput evacuation routes and exits. This density can range from 1 to 10–12 people / m2 for adults and up to 20–25 people / m2 for schoolchildren.

At the suggestion of A.I. Milinsky, the flux density is measured as the ratio of the part of the area of ​​the passages occupied by people to total area passages. This value characterizes the degree to which evacuation routes are filled with evacuees. The part of the area of ​​the aisles occupied by people is determined as the sum of the areas of the horizontal projections of each person (Appendix E, table EL). The area of ​​the horizontal projection of one person depends on age, character, clothing and ranges from 0.04 to 0.126 m 2. In each individual case, the projection area of ​​one person can be defined as the area of ​​an ellipse:

(1)

where a- person's width, m; with- its thickness, m

The width of an adult at the shoulders ranges from 0.38 to 0.5 m, and the thickness is from 0.25 to 0.3 m. Bearing in mind the different heights of people and some compressibility of the flow due to clothing, the density may in some cases exceed 1 mm. This density will be called relative, or dimensionless, and denote by D o.

Due to the fact that there are people of different ages, sexes and different configurations in the flow, the data on the flow density represent, to a certain extent, averaged values.

For calculations of forced evacuation, the concept is introduced calculated density of human streams. The estimated density of human flows means highest value density, possible when moving on any part of the evacuation route. The maximum possible density is called the limit. The limiting value is understood to mean such a density value, above which mechanical damage to the human body or asphyxiation is caused.

If necessary, you can go from one density dimension to another. In this case, you can use the following ratios:

Where f– the average size projection area of ​​one person, m / person;

a- the width of a person, m.

With massive human flows, the stride length is limited and depends on the flow density. If we take the average stride length of an adult to be 70 cm, and the length of the foot equal to 25 cm, then the linear density at which movement with the indicated stride length is possible will be:

0,7+ 0,25 = 0,95.

In practice, it is believed that a step of 0.7 m in length will remain at a linear density of 0.8. This is due to the fact that in case of mass flows, a person moves his leg between those in front, which contributes to the preservation of the step daina.

Travel speed. Surveys of travel speeds at limiting densities have shown that the minimum speeds on the horizontal sections of the track range from 15 to 17 m / min. The design speed of movement, legalized by the design standards for premises with a massive presence of people, is taken equal to 16 m / min.

On sections of the evacuation route or in buildings where the density of flows during forced movement is known to be less than the limit values, the speed of movement will be correspondingly higher. In this case, when determining the speed of forced movement, one proceeds from the length and frequency of a person's stride. For practical calculations, the speed of movement can be determined by the formula:

(4)

where NS- the number of steps per minute equal to 100.

The speed of movement at the limiting densities on the stairs downwards was 10 m / min, and on the stairs upwards - 8 m / min.

Outputs throughput. The specific throughput of exits is the number of people passing through an exit 1 m wide in 1 minute.

The smallest value of the specific throughput, obtained empirically, at a given density is called the calculated specific throughput. The specific throughput of the outlets depends on the width of the outlets, the density of the traffic and the ratio of the width of the traffic to the width of the outlet.

The norms set the throughput of doors up to 1.5 m wide, equal to 50 people / m-min, and 60 people / m-min with a width of more than 1.5 m (for maximum densities).

Dimensions (edit) emergency exits. In addition to the size of evacuation routes and exits, the norms regulate their design and planning solutions, ensuring the organized and safe movement of people.

Fire hazard production processes v industrial buildings characterized by physicochemical properties substances generated in production. Production of categories A and B, in which liquids and gases circulate, pose a particular danger in case of fires due to the possibility of rapid spread of combustion and smoke from buildings, therefore the length of the paths for them is the smallest. In production of category B, where solid combustible substances are circulated, the rate of propagation of combustion is less, the evacuation period can be slightly increased, and therefore, the length of the evacuation routes will be longer than for production of categories A and B. In production of categories D and D located in buildings of I and II degrees of fire resistance, the length of escape routes is not limited (to determine the category of a building, see Appendix A).

When standardizing, we proceeded from the fact that the number of evacuation routes, exits and their sizes must simultaneously satisfy four conditions:

1) the greatest actual distance from the possible place of stay of a person along the line of free passages or from the door of the most distant room 1 f to the nearest emergency exit must be less than or equal to the required by the standards 1 tr

2) the total width of emergency exits and stairs provided by the project, d f must be greater than or equal to the required norm

3) the number of emergency exits and stairs, for safety reasons, should, as a rule, be at least two.

4) the width of emergency exits and stairs should not be less or more than the values ​​stipulated by the norms.

Typically, in industrial buildings, the length of escape routes is measured from the most distant workplace to the nearest emergency exit. Most often, these distances are normalized within the first stage of evacuation. This indirectly increases the total duration of the evacuation of people from the building as a whole. In multi-storey buildings, the length of escape routes in rooms will be less than in single-storey buildings. This absolutely correct position is given in the norms.

The degree of fire resistance of a building also affects the length of escape routes, since it determines the rate of combustion propagation along structures. In buildings of I and II degrees of fire resistance, the length of the evacuation routes, all other things being equal, will be greater than in buildings of III, IV and V degrees of fire resistance.

The fire resistance of buildings is determined by the minimum fire resistance limits building structures and maximum limits the spread of fire along these structures, when determining the degree of fire resistance, it is necessary to use Appendix B.

The length of escape routes for public and residential buildings is provided as the distance from the doors of the most remote premises to the outside or to the staircase with the exit directly or through the lobby. Usually, when assigning the value of the maximum removal, the purpose of the building and the degree of fire resistance are taken into account. According to SNiP P-L.2-62 “ Public buildings», The length of the escape routes to the exit to the stairwell is insignificant and meets the safety requirements.

1. Calculation of the permissible duration of evacuation in case of fire

In the event of a fire, the danger to humans is high temperatures, a decrease in the oxygen concentration in the indoor air and the possibility of loss of visibility due to smoke from buildings.

The time to reach critical temperatures for humans and oxygen concentrations in a fire is called the critical duration of the fire and is indicated.

The critical duration of a fire depends on many variables:

(1.1)

where is the volume of air in the building or room under consideration, m 3;

with - specific isobaric heat capacity of gas, kJ / kg-deg;

t Kp – temperature critical for humans, equal to 70 ° С;

t H – initial air temperature, ° С;

– the coefficient characterizing heat loss for heating structures and surrounding objects is taken on average equal to 0.5;

Q – heat of combustion of substances, kJ / kg, (Appendix B);

f - combustion surface area, m 2;

NS- weight burning rate, kg / m 2 -min (Appendix B);

v – linear speed of fire propagation over the surface of combustible substances, m / min (Appendix D).

To determine the critical duration of a fire by temperature in industrial buildings using flammable and combustible liquids, you can use the formula obtained on the basis of the heat balance equation:

The free volume of the room corresponds to the difference between the geometric volume and the volume of equipment or objects inside. If it is impossible to calculate the free volume, it is allowed to take it equal to 80% of the geometric volume.

Specific heat capacity of dry air at atmospheric pressure 760 mm. rt. Art., according to tabular data is 1005 kJ / kg-deg at temperatures from 0 to 60 ° C and 1009 kJ / kg-deg at temperatures from 60 to 120 ° C.

With regard to industrial and civil buildings using solid combustible substances, the critical duration of a fire is determined by the formula:

(1.3)

By reducing the concentration of oxygen in the air of the room, the critical duration of the fire is determined by the formula:

(1.4)

where W02 is the oxygen consumption for the combustion of 1 kg of combustible substances, m / kg, according to the theoretical calculation is 4.76 ogmin.

The linear speed of fire propagation during fires, according to VNIIPO, is 0.33-6.0 m / min, more accurate data for different materials are presented in Appendix D.

The critical duration of a fire for loss of visibility and for each of the gaseous toxic combustion products is longer than the previous ones, therefore, they are not taken into account.

From the values ​​of the critical duration of the fire obtained as a result of calculations, the minimum is selected:

(1.5)

The permissible duration of evacuation is determined by the formulas:

where and – correspondingly permissible duration

evacuation and critical duration of a fire during evacuation, min,

m – degree-dependent safety factor fire protection building, its purpose and the properties of combustible substances formed in production or which are the subject of furnishings of premises or their decoration.

For entertainment enterprises with a grate stage separated from the auditorium by a fire wall and a fire curtain, with fire retardant treatment flammable substances on the stage, the presence of stationary and automatic extinguishing means and fire warning devices m = 1,25.

For entertainment enterprises in the absence of a grate stage (cinemas, circuses, etc.) m = 1,25.

For entertainment companies with a stage for concert performances T =1,0.

For spectacular enterprises with a grate stage and in the absence of a fire curtain and automatic extinguishing and fire warning devices T = 0,5.

In industrial buildings with automatic extinguishing and fire warning equipment t = 2,0.

In industrial buildings in the absence of automatic extinguishing means and fire warning t = 1,0.

When placing industrial and other processes in buildings of III degree of fire resistance T = 0,65–0,7.

The critical duration of a fire for the building as a whole is set depending on the time of penetration of combustion products and the possible loss of visibility in the communication rooms located before leaving the building.

Experiments carried out on wood combustion have shown that the time after which a loss of visibility is possible depends on the volume of the premises, the weight rate of burning of substances, the speed of flame propagation over the surface of substances and the completeness of combustion. In most cases, a significant loss of visibility during the combustion of solid combustible substances occurred after temperatures that were critical for humans appeared in the room. The largest number smoke-forming substances occurs in the smoldering phase, which is characteristic of fibrous materials.

When fibrous substances are burned in a loosened state, intense combustion from the surface takes place for 1–2 min, after which smoldering begins with violent smoke formation. When burning solid wood-based products, smoke formation and the spread of combustion products in adjacent rooms observed in 5-6 minutes.

Observations have shown that at the beginning of the evacuation, the decisive factor in determining the critical duration of a fire is the effect of heat on the human body or a decrease in oxygen concentration. This takes into account that even a slight smoke, in which satisfactory visibility is still maintained, can have a negative psychological impact on evacuees.

As a result, evaluating the critical duration of a fire to evacuate people from the building as a whole, the following can be established.

In case of fires in civil and industrial buildings, where the main combustible material is cellulosic materials (including wood), the critical duration of the fire can be taken equal to 5–6 minutes.

In case of fires in buildings where fibrous materials circulate in a loosened state, as well as flammable and flammable liquids - from 1.5 to 2 minutes.

In buildings in which the evacuation of people cannot be ensured within the specified time, measures should be taken to create smoke-free escape routes.

In connection with the design of high-rise buildings, the so-called smoke-free stairs began to be widely used. Currently, there are several options for the device smoke-free stairs. The most popular option is with the entrance to the staircase through the so-called air zone. Balconies, loggias and galleries are used as an air zone (Figure 2, a, b).

Figure 2 - Smoke-free stairs: a - entrance to the staircase through the balcony; b - entrance to the staircase through the gallery.

2. Calculation of the evacuation time

The duration of the evacuation of people before leaving the building is determined by the length of the escape routes and the throughput of doors and stairs. The calculation is carried out for the conditions that on the evacuation routes the flux densities are uniform and reach maximum values.

According to GOST 12.1.004-91 (Appendix 2, p. 2.4), the total time of evacuation of people is the sum of the interval "time from the occurrence

fire before the start of evacuation of people ", tn e, and the estimated time of evacuation, t p , which is the sum of the time of movement of the human flow in individual sections ( t ,) its route from the location of people at the time of the beginning of the evacuation to the evacuation exits from the premises, from the floor, from the building.

The need to take into account the time of the beginning of the evacuation for the first time in our country was established by GOST 12.1.004–91. Studies carried out in various countries have shown that when receiving a signal about a fire, a person will investigate the situation, notify about the fire, try to fight the fire, collect things, provide assistance, etc. The average value of the delay time for the start of evacuation (in the presence of a warning system) can be low, but it can also reach relatively high values. For example, the value of 8.6 microns was recorded during a training evacuation in a residential building, 25.6 minutes in the building of the World Shopping Center in a fire in 1993.

In view of the fact that the duration of this stage significantly affects the total evacuation time, it is very important to know what factors determine its value (it should be borne in mind that most of these factors will also affect throughout the entire evacuation process). Based on the existing work in this area, the following can be distinguished:

Human condition: persistent factors (limitation of the sense organs, physical limitations, temporary factors (sleep / wakefulness), fatigue, stress, as well as a state of intoxication);

Notification system;

Staff actions;

Social and family ties of a person;

Firefighting training and education;

Building type.

The delay time for the start of the evacuation is taken according to Appendix D.

Estimated time of evacuation of people ( t P ) should be defined as the sum of the time of movement of the flow of people along individual sections of the path t f :

......................................................... (2.1)

where is the delay time for the start of evacuation;

t 1 - time of movement of the flow of people in the first section, min;

t 2 , t 3 ,.......... t i- time of movement of the flow of people on each of the following sections of the path after the first, min.

When calculating, the entire path of movement of the human flow is divided into sections (passage, corridor, doorway, staircase, vestibule) with length /, and width bj . The starting areas are the aisles between workstations, equipment, rows of chairs, etc.

When determining the estimated time, the length and width of each section of the escape route are taken according to the project. Path length along flights of stairs, as well as on ramps, it is measured along the length of the march. Path length in doorway taken to be zero. The opening located in the wall with a thickness of more than 0.7 m, as well as the vestibule should be considered independent site a horizontal path of finite length.

Time of movement of the flow of people along the first section of the path ( t ;), min, calculated by the formula:

where – length of the first track section, m;

- the value of the speed of movement of the flow of people along the horizontal path in the first section, is determined depending on the relative density D, m 2 / m 2.

The density of the flow of people ( D \) on the first section of the path, m / m, is calculated by the formula:

where – the number of people in the first section, people;

f is the average area of ​​the horizontal projection of a person, taken according to Table E. 1 of Appendix E, m 2 / person;

and – length and width of the first section of the track, m.

The speed V / of the movement of the flow of people on the sections of the path following the first is taken according to Table E.2 of Appendix E, depending on the value of the intensity of movement of the flow of people for each of these sections of the path, which is calculated for all sections of the path, including for doorways, according to the formula:

where , - the width of the considered i-th and the preceding section of the track, m;

, – values ​​of the traffic intensity of the human flow along the considered i-th and previous sections of the path, m / min.

If the value , determined by formula (2.4) is less than or equal to the value q max , then the time of movement along the section of the path () per minute: in this case, the values q max , m / min, should be taken according to table 2.1.

Table 2.1 - Traffic intensity of people

If the value q h defined by formula (2.4) is greater than q max , then the width bj of this section of the path should be increased by such a value at which the condition is met:

If it is impossible to satisfy condition (2.6), the intensity and speed of movement of the human flow along the section of the path i determined according to Table E.2 of Appendix E with the value D = 0.9 or more. In this case, the time delay in the movement of people due to the formed congestion should be taken into account.

When merging at the beginning of the site i two or more human streams (Figure 3) traffic intensity ( }, m / min, calculated by the formula:

(2.7)

- traffic intensity of human streams merging at the beginning of the section /, m / min;

i – width of the path sections of the confluence, m;

– width of the track section under consideration, m

If the value determined by formula (2.7) is greater than q max , then the width of this section of the track should be increased by such an amount that condition (2.6) is met. In this case, the time of movement on the site i is determined by formula (2.5).

The intensity of traffic in a doorway with a width of less than 1.6 m is determined by the formula:

Where b is the width of the opening.

The time of movement through the opening is defined as the quotient of dividing the number of people in the stream by the throughput of the opening:

Figure 3 - Merging human streams

3. Calculation procedure

· Select the minimum from the calculated critical fire durations and use it to calculate the permissible evacuation duration according to formula (1.6).

· Determine the estimated time of evacuation of people in case of fire, using the formula (2.1).

· Compare the estimated and permissible evacuation time, draw conclusions.

4. Calculation example

It is necessary to determine the time of evacuation from the office of employees of the "Obus" enterprise in the event of a fire in the building. Administrative building panel type, not equipped with an automatic alarm and fire warning system. The building is two-storey, has dimensions in plan of 12x32 m, in its corridors 3 m wide there are schemes for evacuating people in case of fire. An office with a volume of 126 m 3 is located on the second floor in the immediate vicinity of the staircase leading to the first floor. The stairwells are 1.5 m wide and 10 m long. 7 people work in the office. A total of 98 people work on the floor. 76 people work on the ground floor. The evacuation scheme from the building is shown in Figure 4.

Figure 4 - Scheme of evacuation of employees of the enterprise "Obus": 1,2,3,4 - stages of evacuation

4.1 Calculation of the evacuation time

4.1.2. The critical duration of a fire in terms of temperature is calculated using the formula (1.3), taking into account the furniture in the room:

4.1.3 The critical duration of a fire in terms of oxygen concentration is calculated using the formula (1.4):

4.1.4 Minimum fire duration by temperature
is 5.05 minutes. Allowable evacuation time for a given
premises:

4.1.5 The delay time for the start of evacuation is taken as 4.1 minutes according to Table D. 1 of Appendix D, taking into account that the building does not have automatic system alarms and fire alarms.

4.1.6 To determine the time of movement of people along the first section, taking into account overall dimensions cabinet 6x7 m, the density of traffic in the first section is determined by the formula (2.3):

.

According to table E.2 of Appendix E, the speed of movement is 100 m / min, the intensity of movement is 1 m / min, i.e. time of movement along the first section:

4.1.7 The length of the doorway is taken to be zero. The greatest possible traffic intensity in the opening under normal conditions is g mffic = 19.6 m / min, the traffic intensity in the opening with a width of 1.1 m is calculated by the formula (2.8):

q d = 2,5 + 3,75 b = 2.5 + 3.75 1.1 = 6.62 m / min,

q d therefore, movement through the opening is unimpeded.

The time of movement in the opening is determined by the formula (2.9):

4.1.8. Since 98 people work on the second floor, the density of the people flow on the second floor will be:

According to table E2 of Appendix E, the speed of movement is 80 m / min, the intensity of movement is 8 m / min, i.e. time of movement along the second section (from the corridor to the stairs):

4.1.9 To determine the speed of movement on the stairs, the traffic intensity in the third section is calculated according to the formulas (2.4):

,

This shows that the speed of the flow of people on the stairs is reduced to 40 m / min. Time of moving down the stairs (3rd section):

4.1.10 When moving to the first floor, mixing with the flow of people moving along the first floor occurs. Traffic density for the first floor:

the traffic intensity will be about 8 m / min.

4.1.11. When moving to the 4th section, there is a merger of human streams, therefore, the intensity of movement is determined by the formula (2.7):

According to table E.2 of Appendix E, the speed of movement is 40 m / min, therefore the speed of movement along the corridor of the first floor:

4.1.12 The tambour when entering the street has a length of 5 meters, on this section the maximum density of the human flow is formed, therefore, according to the application, the speed drops to 15 m / min, and the time of movement along the tambour will be:

4.1.13 At the maximum density of the human flow, the intensity of traffic through the doorway to the street with a width of more than 1.6 m - 8.5 m / min, the time of movement through it:

4.1.13 Estimated time of evacuation is calculated by the formula (2.1):

4.1.14 Thus, the estimated time of evacuation from the offices of the Obus enterprise is longer than the permissible one. Therefore, the building in which the enterprise is located must be equipped with a fire warning system, automatic signaling devices.

List of sources used

1 Labor protection in construction: Textbook. for universities / N.D. Zolotnitsky [and others]. - M .: graduate School, 1969 .-- 472 p.

2 Labor safety in construction (Engineering calculations for the discipline "Life Safety"): Tutorial/ D.V. Koptev [and others]. - M .: Publishing house ASV, 2003 .-- 352 p.

3 Fetisov, P.A. Fire safety handbook. - M .: Energoizdat, 1984 .-- 262 p.

4 Table of physical quantities: Handbook. / I.K. Kikoin [and others]

5 Schreiber , D. Fire extinguishing agents. Physicochemical processes when burning and extinguishing. Per. with him. - M .: Stroyizdat, 1975 .-- 240 p.

6 GOST 12.1.004–91. SSBT. Fire safety. General requirements... - Introduce. from 01.07.1992. - M .: Publishing house of standards, 1992.-78 p.

7 Dmitrichenko A.S. A new approach to the calculation of forced evacuation of people during fires / A.S. Dmitrichenko, S.A. Sobolevsky, S.A. Tatarnikov // Fire and explosion safety, No. 6. - 2002. - S. 25–32.

Appendix A

Appendix B

Table B.1 - Degree of fire resistance for various buildings

Appendix B

Table B.1 - Average burnup rate and heat of combustion of substances and materials

Appendix D

Table D.1 - Linear speed of flame propagation on the surface of materials

Appendix D

Table D. 1 - Delay time for the start of evacuation

Appendix E

Table E.1 - Human projection area

Table E.2 - Dependence of the speed and intensity of traffic on the density of the human flow

2. Or here's another question: "Why do the state examination bodies require blocking one of the emergency exits according to the fire scenario for public buildings designed according to SNiP 2.08.02-89 *?"

SNiP 2.08.02-89 * are still valid for a very large range of buildings. And for compliance with the requirements of SNiP 21-01-97 *, these standards were not processed. They must be applied "in conjunction" with SNiP 2.01.02-85 *, as clearly follows from the preamble (preface) to SNiP 21-01-97 *. In SNiP 2.01.02-85 * there is not a word about blocking in the scenarios of one of the outputs, such a requirement is only in clause 6.15 of SNiP 21-01-97 *: “In the presence of two or more emergency exits, the total throughput of all exits, except each one of them must ensure the safe evacuation of all people in the room, on the floor or in the building. " Yes, of course, experts also refer to clause 2.5 of Appendix 2 * to GOST 12.1.004-91 * “... The critical duration of a fire for people on the floor of the fire is determined from the condition that one of the OFP in the floor corridor reaches its maximum permissible values. As a criterion of danger for people above the fire source, the condition for one of the RPF to reach the maximum permissible value in the staircase at the level of the fire floor is considered. " But here it is clearly not said that before these values ​​are reached, it is impossible to undertake an evacuation into any stairwells ... Nonsense, in a word. This issue also causes the experts to crash the program.
Uncertain answers: "Well, there are people there, so it must be the same, as for warehouses, and for industrial buildings, and for offices ..." (SNiPs for which they work "in conjunction" with SNiP 21-01-97 *), cause a certain degree of understanding, but after all, the experts and employees of the Ministry of Regional Development should apply with a petition about the inconsistencies of the norms with the current realities to their leadership, so that they submit documents carefully prepared by experts for the introduction and approval of changes. But this is a utopia. As always, no one needs anything ... All for show, for safety net, for "excuse". Easier to puzzle designers.

3. Another question: "If there is no GOST, then what is required from the calculations themselves?"

An absolutely correct and sensible remark was made by the statistician ®: “the effect of one of the toxic combustion products (I don’t remember which now) always turns out to be negative - this suggests that there is a mistake in the formula (I don’t say - only my speculations)”.
No, this is not speculation, you have noticed everything correctly. On 01.10.1993, changes were made to GOST 12.1.004-91 (after which GOST became known as GOST 12.1.004-91 * (with an asterisk)), where they "lost" the unfortunate unit in the formula for calculating the achievement of maximum permissible values RPP for elevated temperature, i.e. in GOST 12.1.004.-91 * edition of 1996, and then in 2002, which is currently in force, changes have been made to formula (25) GOST 12.1.004-91, and formula (25) * GOST 12.1.004 -91 * looks different, without the number "1" under the logarithm sign.
An expert on one of the projects remarked: “Well, yes, this is a mistake by GOST !!! We must count according to the old formula. " Now I make two calculations according to this formula (so that no expert asked any questions), with an idiotic wording: “so, they say, it was according to the requirements of GOST 12.1.004-91 * and here is the result of the calculation, and now we will calculate according to the requirements of GOST 12.1. 004-91 * with changes to this formula, and here is the result of the calculation. We accept the worst of the two results, that is, not negative. " Someone's booze and the unit from the formula, removed as a result of this binge, led to an always negative result according to the formula for calculating the achievement of maximum permissible RPP values ​​for elevated temperatures and turned into a smut for the designers.

4. “Why then the norms, if you still need to make a calculation, and based on it, take all the parameters of the escape routes, or then frantically adjust the number of people according to the technology to the adopted space-planning decisions, so that they“ agree ”according to the always controversial calculation? Often we do not fit into the norms, we need to expand broader than the requirements of the norms - why then the norms are not as strict as the calculation data? " - I have not been able to give her an intelligible answer to these questions of our architect for a year. And how to tell architects right off the bat, without making calculations, what passages should be? Relatively honest calculation (and he is always honest only relatively, because of the necessary evacuation time) often get insane values. By balancing, you get a clear result. A beautiful, indisputable and very honest, without wisdom, calculation, with standardized aisles, is 100% obtained only in large warehouses with painted technology under, as always, a small number of employees, or in offices with small offices and not long corridors.

Conclusion: but there is no conclusion. It is difficult to draw conclusions from nonsense.

Maybe I forgot to mention something, don't blame me. Correct if that ...

With respect to members of the forum, H * o * B * a * T * o * R.

All documents presented in the catalog are not their official publication and are intended solely for informational purposes. Electronic copies of these documents can be distributed without any restrictions. You can post information from this site to any other site.

MINISTRY OF INTERNAL AFFAIRS OF THE USSR

ALL-UNION ORDER "SIGN OF HONOR"
RESEARCH INSTITUTE
FIRE DEFENSE.

APPROVED

Head of VNIIPO Ministry of Internal Affairs of the USSR

D. I. Yurchenko

September 29, 1989

CALCULATION OF THE NEEDED TIME
EVACUATION OF PEOPLE FROM THE ROOMS
IN THE FIRE

MOSCOW 1989

Calculation of the required time to evacuate people from premises in case of fire: Recommendations. - M .: VNIIPO Ministry of Internal Affairs of the USSR, 1989.

The procedure for calculating the required time, evacuating people from premises for various purposes in the event of a fire in them is stated.

When solving the problem, the following hazardous fire factors were taken into account: increased ambient temperature; smoke leading to loss of visibility; toxic gases; reduced oxygen concentration. The required evacuation time was determined according to the condition that one of these factors reached the maximum permissible value for a person.

Designed for engineering and technical workers of the fire department, teachers, students of fire-technical educational institutions, employees of research, design, construction organizations, etc. institutions.

Tab. 4, appendix 1, bibliography: 4 titles.

INTRODUCTION

A characteristic feature of modern construction is the increase in the number of buildings with a massive presence of people. These include indoor cultural and sports complexes, cinemas, clubs, shops, industrial buildings, etc. Fires in such premises are often accompanied by injury and death of people. First of all, this applies to rapidly developing fires, which pose a real danger to humans within a few minutes after their occurrence and are characterized by an intense impact on people of hazardous fire factors (MF). The most reliable way to ensure the safety of people in such conditions is the timely evacuation from the premises in which the fire broke out.

In accordance with GOST 12.1.004-85. SSBT. "Fire safety. General requirements", each object must have such a space-planning and technical design so that the evacuation of people from the premises was completed before the RPM reaches the maximum permissible values. In this regard, the number, size and design of escape routes and exits are determined depending on the required evacuation time, i.e. the time during which people must leave the premises without being exposed to fire hazardous to life and health / /. The data on the required evacuation time is also the initial information for calculating the level of ensuring the safety of people in case of fires in buildings. Failure to correctly determine the required evacuation time can lead to inappropriate design decisions and increased building costs, or inadequate human safety in the event of a fire.

In accordance with the recommendations of the work / /, the required evacuation time is calculated as the product of the critical fire duration for a person by the safety factor. The critical duration of a fire means the time after which a dangerous situation arises due to the achievement of one of the OFPs of the maximum permissible value for a person. In this case, it is assumed that each hazardous factor affects a person independently of the others, since the complex impact of various qualitative and quantitative combinations of MFs that change over time, characteristic of the initial period of fire development, is currently not possible to assess. The safety factor takes into account the possible error in solving the problem. It is taken equal to 0.8 / /.

Thus, in order to determine the required time for evacuating people from the premises, it is necessary to know the dynamics of the MF in the zone where people are staying (working zone) and the maximum permissible values ​​for a person for each of them. The number of RPs that pose the greatest danger to people in a room during the initial period of a rapidly developing fire can include: increased ambient temperature; smoke leading to loss of visibility; combustion products are more toxic; reduced oxygen concentration.

The methodology for calculating the required evacuation time, set out in these recommendations, was developed on the basis of theoretical and experimental studies of the dynamics of RP, acting at the critical stage of a fire for a person in rooms for various purposes, carried out at the VNIIPO of the USSR Ministry of Internal Affairs. The values ​​obtained as a result of biomedical studies of the impact on humans of various hazardous factors were used as the maximum permissible levels of RP for humans.

1. GENERAL PROVISIONS

through open openings, only gas is displaced from the room;

the absolute gas pressure in the room does not change during a fire;

the ratio of heat loss in building structures to the thermal power of the fire center is constant in time;

the properties of the environment and the specific characteristics of the material burning in a fire (lower working heat of combustion, smoke-generating capacity, specific output of toxic gases, etc.) are constant;

the time dependence of the burnt-out mass of material is a power-law function.

The proposed method is applicable for calculating the required evacuation time in case of rapidly developing fires in rooms with an average rate of increase in the ambient temperature for the period under consideration of more than 30 deg · min -1. Such fires are characterized by the presence of near-wall circulation jets and the absence of a clear boundary of the smoke layer. The use of calculation formulas for fires with a lower temperature rise rate will lead to an underestimation of the required evacuation time, i.e. to increase the safety margin when solving the problem.

2. METHODOLOGY OF CALCULATING THE NECESSARY EVACUATION TIME OF PEOPLE FROM THE ROOMS IN THE FIRE

2.1. General calculation procedure

Based on the analysis of the design solution of the object, the geometric dimensions of the room and the height of the working areas are determined. The free volume of the room is calculated, which is equal to the difference between the geometric volume of the room and the volume of equipment or objects inside. If it is impossible to calculate the free volume, then it is allowed to take it equal to 80% of the geometric volume / /.

Next, calculation schemes for the development of a fire are selected, which are characterized by the type of combustible substance or material and the direction of the possible propagation of the flame. When choosing calculation schemes for the development of a fire, one should focus primarily on the presence of flammable and combustible substances and materials, the rapid and intense combustion of which cannot be eliminated by the forces of the people in the room. Such substances and materials include: flammable and combustible liquids, loosened fibrous materials (cotton, flax, waste, etc.), hanging fabrics (for example, curtains in theaters or cinemas), decorations in entertainment enterprises, paper, wood chips, some types of polymeric materials (for example, soft polyurethane foam, plexiglass), etc.

For each of the selected fire development patterns, the critical fire duration for a person is calculated by the following factors: elevated temperature; loss of visibility in smoke; toxic gases; reduced oxygen content. The obtained values ​​are compared with each other and from them the minimum is selected, which is the critical duration of the fire no j th design scheme.

Then the most dangerous pattern of fire development in this room is determined. For this purpose, for each of the schemes, the amount of material burned out by the time is calculated m j and compared to c the total amount of this material M j , which can be engulfed in fire according to the considered scheme. Design schemes in which m j> M j are excluded from further analysis. From the remaining design schemes, the most dangerous fire development scheme is selected, in which the critical duration of the fire is minimal.

Learned valuetcrtaken as the critical duration of the fire for the room in question.

By value tcrthe required time for the evacuation of people from this room is determined.

2.1.1. Determination of the geometric characteristics of the room

The geometric characteristics of the room used in the calculation include its geometric volume, the reduced height H and the height of each of the working areas h.

The geometric volume is determined based on the size and configuration of the room. The reduced height is found as the ratio of the geometric volume to the area of ​​the horizontal projection of the room. The height of the working area is calculated as follows:

where h mark - elevation of the mark of the zone where people are located above the floor of the room, m; δ is the difference in floor heights, equal to zero when it is horizontal, m.

It should be borne in mind that people who are at the higher elevation are exposed to the maximum danger in a fire. So, when determining the required time for the evacuation of people from the parterre of an auditorium with an inclined floor, the value h for the parterre, you need to calculate, focusing on the rows of chairs that are far from the stage (located at the highest mark).

2.1.2. The choice of calculation schemes for the development of a fire

The time of occurrence of situations hazardous to humans in the event of a fire in a room depends on the type of combustible substances and materials and the area of ​​combustion, which, in turn, is determined by the properties of the materials themselves, as well as the way they are laid and resolved. Each design scheme for the development of a fire in a room is characterized by the values ​​of two parameters A and n , which depend on the shape of the combustion surface, characteristics of combustible substances and materials and are determined as follows.

1. For burning flammable and combustible liquids spilled on the area F:

when burning a liquid at a steady rate (typical for volatile liquids)

where ψ is the specific steady-state mass rate of liquid burnout, kg · m -2 s -1;

when burning a liquid at an unsteady rate

The critical duration of a fire is determined for a given design scheme

,

where i = 1, 2, ... n - the index of the toxic combustion product.

In the absence of special requirements, the valuesα and E are taken equal to 0.3 and 50 lux, respectively.

2.1.4. Determination of the most dangerous scheme for the development of a fire in a room

After calculating the critical duration of a fire for each of the selected schemes of its development, the amount of burned out by the timetcrj material.

Each value in the considered j -th scheme is compared with the indicator M j ... Design schemes for which m j> M j , as already noted, are excluded from further consideration. The most dangerous one is selected from the remaining design schemes, i.e. the one for which the critical duration is minimal t cr = min (t cr j).

The resulting value t cr is the critical duration of a fire for a given work area in the room in question.

2.1.5. Determining the required evacuation time

The required time for the evacuation of people from a given working area of ​​the room in question is calculated by the formula:

,

where to b- safety factor, to b = 0,8.

Initial data for calculations can be taken from table. - appendices or from reference books.

2.2. Calculation examples

Example 1.Determine the required time for the evacuation of people from the auditorium of the cinema. The length of the hall is 25 m, width - 20 m.The height of the hall from the side of the stage is 12 m, from the opposite side - 9 m. The length of the horizontal section of the butt near the stage at the zero mark is 7 m. The balcony of the auditorium is located at a height of 7 m from the zero marks. A curtain weighing 50 kg is made of fabric with the following characteristics:Q= 13.8 MJ · kg -1; D= 50 Np · m 2 · kg -1; L O 2 , = 1.03 kg · kg -1; L CO2 = 0.203 kg · kg -1; L CO = 0.0022 kg · kg -1; ψ = 0.0115 kg m 2 s -1;V B= 0.3 m · s -1; VG= 0.013 m s -1. Chairs upholstery - polyurethane foam covered with leatherette. The initial temperature in the hall is 25 ° C, the initial illumination is 40 lux, the volume of items and equipment is 200 m 3.

1. Determine the geometric characteristics of the room.

The geometric volume is

.

Reduced height H is defined as the ratio of the geometric volume to the area of ​​the horizontal projection of the room

.

The room contains two working areas: a parterre and a balcony. In accordance with the instructions given in section (), we find the height of each working area

for parterre h = 3 + 1.7 - 0.5 - 3 = 3.2 m;

for balcony h = 7 + 1.7 - 0.5 - 3 = 7.2 m.

Free volume of the room V = 5460 - 200 = 5260 m 3.

2. We select the design schemes of the fire. In principle, two variants of the occurrence and spread of a fire in a given room are possible: along the curtain and along the rows of chairs. However, the ignition of the leatherette upholstery of the chair from a low-calorie source is difficult to implement and can be easily eliminated by the forces of people in the hall.

Consequently, the second scheme is practically unrealistic and disappears.

Specific mass burnup rate ψ × 10 3, kg m 2 s -1

Net calorific value Q, kJ kg -1

Petrol

61,7

41870

Acetone

44,0

28890

Diethyl ether

60,0

33500

Benzene

73,3

38520

Diesel fuel

42,0

48870

Kerosene

48,3

43540

Fuel oil

34,7

39770

Oil

28,3

41870

Ethanol

33,0

27200

Turbine oil (TP-22)

30,0

41870

Isopropyl alcohol

31,3

30145

Isopentane

10,3

45220

Toluene

48,3

41030

Metallic sodium

17,5

10900

Wood (bars) W = 13.7%

39,3

13800

Wood (furniture in residential and office buildings W = 8-10%)

14,0

13800

Loose paper

8,0

13400

Paper (books, magazines)

4,2

13400

Books on wooden shelves

16,7

13400

Film triacetate

9,0

18800

Carbolite products

9,5

26900

SKS rubber

13,0

43890

Natural rubber

19,0

44725

Organic glass

16,1

27670

Polystyrene

14,4

39000

Rubber

11,2

33520

Textolite

6,7

20900

Polyurethane foam

2,8

24300

Staple fiber

6,7

13800

Staple fiber in bales 40 × 40 × 40 cm

2,5

13800

Polyethylene

10,3

47140

Polypropylene

14,5

45670

Cotton in bales ρ = 190 kg m -3

2,4

16750

Loose cotton

21,3

15700

Loose flax

21,3

15700

Cotton + nylon (3: 1)

12,5

16200

Table 2

Linear velocity of flame propagation over the surface of materials

Table 3

Smoke-generating ability of substances and materials

Table 4

Specific output (consumption) of gases during combustion of substances and materials

Cotton + nylon (3: 1)

0,012

1,045

3,55

Turbine oil TP-22

0,122

0,7

0,282

AVVG cables

0,11

0,023

APVG cables

0,150

2. All-Union norms of technological design. Determination of categories of premises and buildings for explosion and fire hazard: ONTP 24-86 / Ministry of Internal Affairs of the USSR; Enter. 01/01/87: Instead of SN 463-74. - M .. 1987. - 25 p.

3. Research and development of a manual for determining the required time for evacuation of people from the halls in case of fire: Report on research / VNIIPO of the USSR Ministry of Internal Affairs; The leader is T.G. Merkushkina. - P.28.D.024.84; No. GR 01840073434; Inv. No. 02860056271. - M. 1984. - 195 p.

4. Methods for calculating the temperature regime of a fire in the premises of buildings for various purposes: Recommendations. - M .: VNIIPO Ministry of Internal Affairs of the USSR. 1988 .-- 56 p.

1. Literature used during the lesson:

FZ No. 123 dated July 22, 2008. "Technical regulations on fire safety requirements"

SNiP 21-01-97 * "Fire safety of buildings and structures."

SNiP 2.08.02-89 * "Public buildings and structures".

SNiP 2.01.02-85 * "Fire safety standards"

2. Detailed lesson plan

№ p / n Educational questions (including control tasks) Time (min.) Content of the educational question, the method of working out and material support (including technical teaching aids), educational questions

1. Introductory part 5 The personnel gathers in the training class of the PCh-1. His readiness for the lesson is checked. The topic of the lesson and its purpose are announced.

Terms and Definitions.

Evacuation is a process of organized independent movement of people out of the premises, in which there is a possibility of exposure to hazardous factors of fire. Evacuation should also be considered the involuntary movement of people belonging to low-mobility groups of the population, carried out by service personnel. Evacuation is carried out along the evacuation routes through evacuation exits. Also in everyday life, the terms fire evacuation, building evacuation are used.

Evacuation of people in case of fire is a forced process of movement of people from an area where there is a possibility of exposure to hazardous factors of a fire

Rescue is the forced movement of people outward when exposed to dangerous fire factors or when there is an immediate threat of this impact. Rescue is carried out independently, with the help of fire departments or specially trained personnel, including the use of rescue equipment, through evacuation and emergency exits.

An evacuation route is a sequence of communication sections leading from places where people are staying to a safe area. Such a path should be protected by the required standards by a complex of space-planning, ergonomic, constructive and engineering solutions, as well as organizational measures.

Evacuation exit - exit to the escape route leading to a safe area in case of fire and meeting safety requirements.

Measures to ensure the protection of escape routes.

Space planning: the shortest distances to emergency exits, their sufficient width, isolation of escape routes from fire and explosive rooms, the ability to move to several emergency exits, etc.

Ergonomic: assignment of the size of escape routes and exits corresponding to the anthropometric dimensions of people, the peculiarities of their movement, rationing of efforts when opening doors, etc.

Constructive: strength, stability and reliability of structures of evacuation routes and exits, standardization of the flammability of finishes on escape routes, height differences on traffic routes, step sizes, slope of stairs and ramps, etc.

Engineering and technical measures: organization of smoke protection, equipment with automatic fire extinguishing installations, design of the required illumination, placement of light indicators, warning system loudspeakers, etc.

Organizational: ensuring the functioning of all emergency exits in the event of a fire and maintaining the space-planning, structural, ergonomic and engineering indicators at the required level, for example: preventing the blockage of escape routes and exits with combustible materials, as well as objects, reducing their throughput, etc.

Description of the evacuation route from the premises of the first to the outside:

1 directly;

2 through the corridor;

3 through the lobby (foyer);

4 through the stairwell;

5 through the corridor and lobby (foyer);

6 through the corridor and staircase;

7 to an adjacent room (except for a room of category A and B), provided with emergency exits

Description of the evacuation route from the premises of any floor, except for the first:

1 directly to the staircase or to the third type of staircase;

2 to the corridor leading directly to the staircase or to the third type of stairs;

3 to the hall (foyer), which has an exit directly to the staircase or to the staircase of the 3rd type;

4 to an adjacent room (except for a room of category A and B), provided with emergency exits

Escape routes within the premises

Standardized parameters are the distance from the most distant point to the exit from the hall, the total width of the exits from the halls (rooms), placement on the floors of the building and capacity.

For auditoriums, the number of continuously installed seats in a row is also normalized: with one-way exit from the row no more than 26, with two-way exit - no more than 50.In cinemas, it is not allowed to design evacuation routes through rooms in which more than 50 people can be. For example, through a room in which the next group of spectators is waiting for a session, through a cafe, etc. In sales areas, the width of the main evacuation passages in the sales area should be from 1.4 to 2.5 m, depending on the area of ​​the sales area.

In sports and entertainment buildings, the number of people per 1m of width of the evacuation routes from the stands of open sports facilities, the number of people evacuated through each exit (hatch) in covered sports facilities, as well as the width of the evacuation routes in the stands are normalized.

Escape routes within a floor

The main standardized parameters for corridors are their width, the length of the paths of movement and the width of the exit from the corridor to the staircase.

As a rule, the length is set depending on the location of the room - between staircases or in a dead-end corridor or hallway and is determined depending on the density of the flow of people, on the degree of fire resistance and the functional purpose of the building.

An analysis of the methodology for standardizing the evacuation process shows that the criterion for determining a room with an exit to a dead-end corridor and a room located between the stairwells is the number of directions for evacuation. One direction of evacuation from the premises is "a room with an exit to a dead-end corridor", two or more - "a room located between the stairwells."

With doors opening from the premises to the corridors, the width of the corridor should be taken as the width of the evacuation route along the corridor, reduced: by half the width of the door leaf - with a one-sided arrangement of the doors; to the width of the door leaf - with two-sided doors.

The number of exits from the premises, from the floor and from the building as a whole.

At least two emergency exits must have:

Premises of class F1.1, designed for the simultaneous stay of more than 10 people;

Premises in the basement and ground floors, designed for the simultaneous stay of more than 15 people; in the premises of the basement and basement floors, intended for the simultaneous stay of 6 to 15 people, one of the two exits may be provided in accordance with the requirements;

Premises designed for the simultaneous stay of more than 50 people;

Premises of class F5 of categories A and B with the number of employees in the most numerous shift of more than 5 people, category C - more than 25 people. or with an area of ​​more than 1000 m2;

Open shelves and platforms in class F5 rooms, intended for equipment maintenance, with a tier floor area of ​​more than 100 m2 - for rooms of categories A and B and more than 400 m2 - for rooms of other categories.

Premises of class F1.3 (apartments), located on two floors (levels), with a height of the upper floor of more than 15 m, must have emergency exits from each floor.

At least two emergency exits must have floors of buildings of the class:

H1.1; Ф3.3; Form 4.1; F4.2;

H1.2; F3; Ф4.3 when the height of the floor is more than 9 m and the number of people on the floor is more than 20;

F1.3 with a total area of ​​apartments on the floor, and for section-type buildings - on the section floor - more than 500 m2; with a smaller area, each apartment located at a height of more than 15 m, in addition to the evacuation one, must have an emergency exit;

At least two evacuation exits must have basement and basement floors with an area of ​​more than 300 m2 or intended for a simultaneous stay of more than 15 people.

The number of emergency exits from a floor must be at least two, if a room is located on it, which must have at least two emergency exits.

The number of emergency exits from the building must not be less than the number of emergency exits from any floor of the building.

In rooms designed for a one-time stay of no more than 50 people. (including the amphitheater or the balcony of the auditorium), with a distance along the passage from the most remote workplace to the emergency exit (door) no more than 25 m, it is not required to design a second emergency exit (door).

Dispersed evacuation exits.

If there are two or more emergency exits, they should be dispersed.

When arranging two emergency exits, each of them must ensure the safe evacuation of all people in the room, on the floor or in the building. If there are more than two emergency exits, the safe evacuation of all people in the room, on the floor or in the building must be provided by all emergency exits.

Evacuation exits should be dispersed. The minimum distance ℓ between the most distant one from the other evacuation exits from the premises should be determined by the formula

ℓ≥1.5√p, where n is the perimeter of the room.

The width of the evacuation exits.

The height of emergency exits in the clear must be at least 1.9 m, width at least:

1.2 m - from premises of class F1.1 with more than 15 people evacuated, from premises and buildings of other classes of functional fire hazard, with the exception of class F1.3, - more than 50 people;

0.8 m - in all other cases.

The width of the outer doors of the staircases and the doors from the staircases to the vestibule must be no less than the calculated one or the width of the stairway set

In all cases, the width of the evacuation exit should be such that, taking into account the geometry of the evacuation route, through the opening or door, it would be possible to freely carry a stretcher with a person lying on it.

The width of the doors of exits from classrooms with an estimated number of students over 15 people. must be at least 0.9 m.

The width of the evacuation exit (door) from the halls without seats for spectators should be determined by the number of people evacuated through the exit according to Table. 10, but not less than 1.2 m in halls with a capacity of more than 50 people.

Corridor width.

The height of the horizontal sections of the escape routes in the clear must be at least 2 m, the width of the horizontal sections of the escape routes and ramps must be at least:

1.2 m - for common corridors, through which more than 15 people can be evacuated from premises of the F1 class, from premises of other classes of functional fire hazard - more than 50 people;

0.7 m - for passages to single workplaces;

1.0 m - in all other cases.

In any case, evacuation routes should be of such width that, taking into account their geometry, it would be possible to carry a stretcher with a person lying on them without hindrance.

The width of the staircase doors.

The width of the flight of the stairs intended for the evacuation of people, including those located in the staircase, must be no less than the calculated one or no less than the width of any escape exit (door) to it, but, as a rule, no less than:

A) 1.35 m - for buildings of class F1.1;

B) 1.2 m - for buildings with more than 200 people on any floor except the first;

B) 0.7 m - for stairs leading to single workstations;

D) 0.9 m - for all other cases.

The width of the landing should be at least the width of the march, and in front of the entrances to the elevators with swing doors - at least the sum of the width of the march and half the width of the elevator door, but not less than 1.6 m.

Intermediate platforms in a straight flight of stairs must have a width of at least 1 m.

Doors overlooking the staircase, in the open position, should not reduce the width of staircases and flights.

The width of the staircase in public buildings should be at least the width of the exit to the staircase from the most populated floor, but not less, m:

1.35 - for buildings with more than 200 people staying on the most populated floor, as well as for buildings of clubs, cinemas and medical institutions, regardless of the number of seats;

1,2 - for other buildings, as well as in the buildings of cinemas, clubs leading to premises not associated with the stay of spectators and visitors, and in buildings of medical institutions leading to premises not intended for the stay or visiting of patients;

0.9 - in all buildings leading to a room with up to 5 people simultaneously staying in it.

An intermediate platform in a straight flight of stairs must have a width of at least 1 m.

The width of the landings must be at least the width of the march.

Door opening direction

Doors on escape routes should open in the direction of the exit from the building.

Doors to balconies, loggias (with the exception of doors leading to the air zone of smoke-free staircases of the 1st type) and to the areas of external stairs intended for evacuation, doors from rooms with a simultaneous stay of no more than 15 people, doors from storage rooms with an area of ​​no more than 200 m2 and sanitary facilities are allowed to be designed with interior opening.

No smoke in the corridors.

Corridors with a length of more than 60 m should be separated by partitions with self-closing doors located at a distance of no more than 60 m from one another and from the ends of the corridor.

In the ward buildings of medical institutions, the corridors should be separated by type 2 fire partitions with a distance between them no more than 42 m.

Escape routes by stairs and ramps

On the escape routes, it is not allowed to arrange spiral staircases, staircases completely or partially curved in the plan, as well as run-in and curvilinear steps, steps with different tread widths and different heights within the staircase and staircase march.The width and slope of staircases and ramps are normalized.

The slope is determined by the ratio H / L, for example, if H = 1.5m, L = 3m, the slope of the stairs is 1: 2

The width of the tread on the stairs should, as a rule, be at least 25 cm, and the height of the step should be no more than 22 cm.

The number of climbs in one march is normalized. For example, for public buildings, there should be at least 3 and no more than 16 rises between sites. In single-flight staircases, as well as in one flight of two- and three-flight staircases, no more than 18 rises are allowed within the first floor. Current standards require that the width of the site be at least the width of the flight of stairs, and the width of the staircase must be at least the width of the exit to staircase, otherwise it is likely that the conditions of unhindered movement are violated.

Stairwells should have an exit to the area adjacent to the building directly or through the lobby, separated from the adjoining corridors by partitions with doors.

Exits from the basement and basement floors, which are evacuation, should, as a rule, be provided directly to the outside, separated from the general staircases of the building. It is allowed to provide evacuation exits from the basements through common staircases with a separate exit to the outside, separated from the rest of the staircase by a deaf fire-prevention partition of the 1st type.

Indoor open stairs are widely used in public buildings, for example. However, due to their increased fire hazard, their use is limited and is made dependent on the degree of fire resistance, the purpose of the building (in hospitals of medical institutions, open stairs are not included in the calculation of the evacuation of people in case of fire). When using internal open stairs in the building, the norms introduce additional requirements for the space-planning solutions of the building: separation of premises with such a staircase from adjacent corridors and other premises by fire partitions, an automatic fire extinguishing device throughout the building, limiting the number of internal open stairs, additional closed stairwells, the exit from which is provided directly to the outside. 3. Maintenance of evacuation routes and exits.

Evacuation routes and exits must be constantly supported not to be blocked by anything, and in the event of a fire, to guarantee during the evacuation of people who are in the premises of houses and the maintenance of escape routes and exits.

Doors on escape routes should open in the direction of exiting houses (premises).

In the presence of people in the room, the doors of the emergency exits can only be closed by internal locks, which can be easily unlocked.

Carpets, carpets and other floor coverings must be securely attached to the floor and be optimally safe in relation to the toxicity of combustion products, have a moderate smoke extraction capacity in accordance with current regulations.

Stairways and platforms must have serviceable railings.

Emergency lighting fixtures should be switched on at dusk if people are in the house.

In the case of people, escape routes that do not have natural lighting must be constantly illuminated with electric light.

It is prohibited:

Arrange thresholds, performances, turnstiles, sliding doors, lifting doors, such that rotate, and other devices on the escape routes, which impede the free evacuation of people;

Clutter corridors, walkways, staircases and landings, lobbies, halls, vestibules and the like with furniture, equipment, various materials, even if they do not reduce the standard width;

To hammer, weld, lock, on padlocks, bolted joints and other locks that are difficult to open from the inside, external escape doors of buildings;

Use on the escape routes (except for buildings of the V degree of fire resistance) combustible materials for facing walls and ceilings, as well as stairs and landings;

Place wardrobes, clothes hangers in the vestibules of exits, adapt them for trade, as well as storage, including temporary storage, of any inventory and material;

Clutter up the exits with furniture, equipment and other items. external escape stairs;

Arrange premises for any purpose in stairwells, in particular kiosks, stalls;

Place barns, booths, stalls and the like in the elevator halls;

To remove the doors of lobbies, halls, vestibules and stairwells provided for by the project;

Remove devices for self-closing doors, staircases, corridors, halls, vestibules, and the like, as well as fix self-closing doors in the open position;

Hang stands, panels and the like in stairwells on the walls;

Hang mirrors on the walls of staircase landings;

Arrange a slippery floor on escape routes.

4. Calculation of the permissible duration of evacuation in case of fire

In the event of a fire, the danger to humans is high temperatures, a decrease in the oxygen concentration in the indoor air and the possibility of loss of visibility due to smoke from buildings.

The time to reach critical temperatures and oxygen concentrations for humans in a fire is called the critical duration of a fire and is designated. The critical duration of a fire depends on many variables:

Where is the volume of air in the building or room under consideration, m3;

C is the specific isobaric heat capacity of the gas, kJ / kg-deg;

TKp - temperature critical for humans, equal to 70 ° С;

TH is the initial air temperature, ° С;

- the coefficient characterizing the heat loss for heating structures and surrounding objects is taken on average equal to 0.5;

Q is the heat of combustion of substances, kJ / kg;

F — combustion surface area, m2;

P - weight burning rate, kg / m2-min;

V is the linear velocity of fire propagation over the surface of combustible substances, m / min.

To determine the critical duration of a fire by temperature in industrial buildings using flammable and combustible liquids, you can use the formula obtained on the basis of the heat balance equation:

The free volume of the room corresponds to the difference between the geometric volume and the volume of equipment or objects inside. If it is impossible to calculate the free volume, it is allowed to take it equal to 80% of the geometric volume.

Specific heat capacity of dry air at atmospheric pressure 760 mm. rt. Art., according to tabular data is 1005 kJ / kg-deg at temperatures from 0 to 60 ° C and 1009 kJ / kg-deg at temperatures from 60 to 120 ° C.

With regard to industrial and civil buildings using solid combustible substances, the critical duration of a fire is determined by the formula:

By reducing the concentration of oxygen in the air of the room, the critical duration of the fire is determined by the formula:

Where W02 is the oxygen consumption for the combustion of 1 kg of combustible substances, m / kg, according to the theoretical calculation is 4.76 ogmin.

The linear speed of fire propagation during fires, according to VNIIPO, is 0.33–6.0 m / min, more accurate data for different materials are presented in Appendix D.

The critical duration of a fire for loss of visibility and for each of the gaseous toxic combustion products is longer than the previous ones, therefore, they are not taken into account.

From the values ​​of the critical duration of the fire obtained as a result of calculations, the minimum is selected:

The permissible duration of evacuation is determined by the formulas:

Where and - respectively the permissible duration

Evacuations and the critical duration of a fire during evacuation, min,

M is the safety factor, depending on the degree of fire protection of the building, its purpose and the properties of combustible substances generated in production or being the subject of furnishing of premises or their decoration.

For entertainment enterprises with a grate stage, separated from the auditorium by a fire wall and a fire curtain, with fire retardant treatment of combustible substances on the stage, the presence of stationary and automatic extinguishing means and fire warning devices m = 1.25.

For entertainment enterprises in the absence of a grate stage (cinemas, circuses, etc.) m = 1.25.

For entertainment enterprises with a stage for concert performances, t = 1.0.

For entertainment enterprises with a grate stage and in the absence of a fire curtain and automatic fire extinguishing and warning equipment, m = 0.5.

In industrial buildings in the presence of means of automatic extinguishing and fire warning t = 2.0.

In industrial buildings, in the absence of automatic extinguishing and fire warning equipment, t = 1.0.

When placing production and other processes in buildings of III degree of fire resistance, t = 0.65–0.7.

The critical duration of a fire for the building as a whole is set depending on the time of penetration of combustion products and the possible loss of visibility in the communication rooms located before leaving the building.

Experiments carried out on wood combustion have shown that the time after which a loss of visibility is possible depends on the volume of the premises, the weight rate of burning of substances, the speed of flame propagation over the surface of substances and the completeness of combustion. In most cases, a significant loss of visibility during the combustion of solid combustible substances occurred after temperatures that were critical for humans appeared in the room. The greatest amount of smoke-forming substances occurs in the smoldering phase, which is characteristic of fibrous materials.

When fibrous substances are burned in a loosened state, intense combustion from the surface takes place for 1–2 min, after which smoldering begins with violent smoke formation. When solid wood-based products are burned, smoke formation and the spread of combustion products into adjacent rooms are observed after 5–6 minutes.

Observations have shown that at the beginning of the evacuation, the decisive factor in determining the critical duration of a fire is the effect of heat on the human body or a decrease in oxygen concentration. At the same time, it is taken into account that even a slight smoke, in which satisfactory visibility is still maintained, can have a negative psychological effect on evacuees.

As a result, evaluating the critical duration of a fire to evacuate people from the building as a whole, the following can be established.

In case of fires in civil and industrial buildings, where the main combustible material is cellulosic materials (including wood), the critical duration of the fire can be taken equal to 5–6 minutes.

In case of fires in buildings where fibrous materials circulate in a loosened state, as well as flammable and flammable liquids - from 1.5 to 2 minutes.

In buildings in which the evacuation of people cannot be ensured within the specified time, measures should be taken to create smoke-free escape routes.

In connection with the design of high-rise buildings, the so-called smoke-free stairs began to be widely used. Currently, there are several options for the device smoke-free stairs. The most popular option is with the entrance to the staircase through the so-called air zone. Balconies, loggias and galleries are used as the air zone.

The duration of the evacuation of people before leaving the building is determined by the length of the escape routes and the throughput of doors and stairs. The calculation is carried out for the conditions that on the evacuation routes the flux densities are uniform and reach maximum values.

According to GOST 12.1.004-91, the total time of evacuation of people is made up of the interval "time from the occurrence

Fire before the start of evacuation of people ", tn e, and the estimated time of evacuation, tp, which is the sum of the time of movement of the human flow in individual sections (t,) of its route from the location of people at the time of the start of evacuation to evacuation exits from the premises, from the floor out of the building.

The need to take into account the time of the beginning of the evacuation for the first time in our country was established by GOST 12.1.004–91. Studies carried out in various countries have shown that when receiving a signal about a fire, a person will investigate the situation, notify about the fire, try to fight the fire, collect things, provide assistance, etc. The average value of the delay time for the start of evacuation (in the presence of a warning system) can be low, but it can also reach relatively high values. For example, the value of 8.6 microns was recorded during a training evacuation in a residential building, 25.6 minutes in the building of the World Trade Center during a fire in 1993.

In view of the fact that the duration of this stage significantly affects the total evacuation time, it is very important to know what factors determine its value (it should be borne in mind that most of these factors will also affect throughout the entire evacuation process). Based on the existing work in this area, the following can be distinguished:

Human condition: persistent factors (limitation of the sense organs, physical limitations, temporary factors (sleep / wakefulness), fatigue, stress, as well as the state of intoxication); warning system;

Staff actions;

Social and family ties of a person;

Firefighting training and education;

Building type.

The delay time for the start of the evacuation is taken according to Appendix D.

The estimated time of evacuation of people (tP) should be determined as the sum of the time of movement of the flow of people along individual sections of the path tf:

Where is the delay time for the start of the evacuation;

T1 is the time of movement of the flow of people in the first section, min;

T2, t3, ti - time of movement of the human flow on each of the following sections of the path after the first, min.

When calculating, the entire path of movement of the human flow is divided into sections (passage, corridor, doorway, staircase, vestibule) with length /, and width bj. The starting areas are the aisles between workstations, equipment, rows of chairs, etc.

When determining the estimated time, the length and width of each section of the escape route are taken according to the project. The length of the path along the flights of stairs, as well as along the ramps, is measured along the length of the flight. The length of the path in the doorway is taken to be zero. An opening located in a wall with a thickness of more than 0.7 m, as well as a vestibule, should be considered an independent section of a horizontal path with a finite length.

The time of movement of the human flow along the first section of the path (t;), min, is calculated by the formula:

Where is the length of the first section of the track, m;

- the value of the speed of movement of the flow of people along the horizontal path in the first section, is determined depending on the relative density D, m2 / m2.

3. Quiz 5 Tools and equipment used in the lesson: classroom

Tasks for independent work of students and preparation for the next lesson: study the requirements of the Charter of the fire service

"___" _____________ 2016

Lesson leader _____________ _____________________

(Full name) date, signature

MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION FEDERAL AGENCY FOR EDUCATION State educational institution of higher professional education "Orenburg State University"

Department of Life Safety

CALCULATION OF EVACUATION TIME

Introduction

1 Calculation of the permissible duration of evacuation in case of fire

2 Calculation of the evacuation time

3 Calculation example

List of sources used

Appendix A. Table AL - Production Categories

Appendix B. Table B.1 - Degree of fire resistance for various buildings

Appendix B. Table B.1 - Average burnup rate and heat of combustion of substances and materials

Appendix D. Table D.1 - Linear velocity of flame propagation on the surface of materials

Appendix E. Table E. 1 - Delay time for the start of evacuation

Appendix E. Table EL - Human projection area. Table E. 2 - The dependence of the speed and intensity of movement on the density of the human flow

Introduction

One of the main methods of protection against the damaging factors of emergencies is the timely evacuation and dispersal of personnel of facilities and the population from dangerous areas and disaster zones.

Evacuation is a set of measures for the organized withdrawal or removal of personnel from facilities from emergency zones or emergency probabilities, as well as life support for those evacuated in the area of ​​deployment.

When designing buildings and structures, one of the tasks is to create the most favorable conditions for human movement in a possible emergency and to ensure its safety. Forced movement is associated with the need to leave a room or building due to a hazard (fire, accident, etc.). Professor V.M. Predtechensky for the first time considered the foundations of the theory of human movement as an important functional process inherent in buildings for various purposes.

Practice shows that forced movement has its own specific features that must be taken into account to preserve the health and life of people. It is estimated that about 11,000 people die in fires in the United States every year. The largest catastrophes with human casualties have recently taken place in the United States. Statistics show that the largest number of victims is caused by fires in buildings with large numbers of people. The death toll in some fires in theaters, department stores and other public buildings has reached several hundred.

The main feature of forced evacuation is that in the event of a fire, already at its very initial stage, a person is in danger as a result of the fact that the fire is accompanied by the release of heat, products of complete and incomplete combustion, toxic substances, collapse of structures, which in one way or another threatens health or even human life. Therefore, when designing buildings, measures are taken so that the evacuation process could be completed at the required time.

The next feature is that the process of movement of people, due to the danger threatening them, instinctively begins simultaneously in one direction in the direction of the exits, with a certain manifestation of physical efforts in some of the evacuees. This leads to the fact that the passages are quickly filled with people at a certain density of human flows. With an increase in the density of streams, the speed of movement decreases, which creates a quite definite rhythm and objectivity of the movement process. If, during normal movement, the evacuation process is arbitrary (a person is free to move at any speed and in any direction), then with a forced evacuation this becomes impossible.

An indicator of the effectiveness of the forced evacuation process is the time during which people can, if necessary, leave individual premises and the building as a whole.

The safety of forced evacuation is achieved if the duration of the evacuation of people from individual rooms or buildings as a whole will be less than the duration of the fire, after which there are exposures that are dangerous to humans.

The short duration of the evacuation process is achieved by constructive, planning and organizational solutions, which are standardized by the corresponding SNiPs.

Due to the fact that during a forced evacuation, not every door, staircase or opening can provide a short-term and safe evacuation (dead-end corridor, a door to an adjacent room without an exit, a window opening, etc.), design standards stipulate the concepts of "emergency exit" and "escape route ".

According to the norms (SNiP P-A. 5–62, p. 4.1) emergency exits doorways are considered if they lead from the premises directly to the outside; into the staircase with access to the outside directly or through the lobby; into a passage or corridor with direct access to the outside or into a staircase; to adjacent rooms on the same floor, which have a fire resistance of at least III degree, do not contain industries related to fire hazard categories A, B and C, and have a direct exit to the outside or to the staircase (see Appendix A).

All openings, including doorways, that do not have the above signs are not considered evacuation and are not taken into account.

TO evacuation routes include those that lead to an emergency exit and ensure safe movement for a certain time. The most common escape routes are walkways, corridors, foyers, and stairs. Communication routes associated with a mechanical drive (elevators, escalators) do not belong to escape routes, since any mechanical drive is associated with energy sources that can fail in a fire or accident.

Emergency exits are those that are not used during normal traffic, but can be used if necessary during a forced evacuation. It has been established that people usually use entrances during forced evacuation, which they used during normal movement. Therefore, in premises with a mass presence of people, emergency exits are not taken into account for evacuation.

The main parameters characterizing the process of evacuation from buildings and structures are:

The density of the flow of people (D);

The speed of movement of the human stream (v);

Path capacity (Q);

Traffic intensity (q);

Length of escape routes, both horizontal and inclined;

Width of evacuation routes .

The density of human flows. The density of human flows can be measured in various units. So, for example, to determine the length of a person's stride and the speed of his movement, it is convenient to know the average length of the section of the evacuation route per person. The stride length of a person is taken equal to the length of the section of the path per person, minus the length of the foot (Figure 1).

Figure 1 - Scheme for determining the step length and linear density

In industrial buildings or premises with low occupancy, the density can be more than 1 m3 / person. The density, measured by the length of the path per person, is usually called linear and is measured in m / person. Let us denote the linear density by D.

A more visual unit for measuring the density of human flows is the density per unit area of ​​the evacuation route and expressed in people / m2. This density is called absolute and is obtained by dividing the number of people by the area of ​​the evacuation route they occupy and is denoted Dr. Using this unit of measurement, it is convenient to determine the capacity of evacuation routes and exits. This density can range from 1 to 10–12 people / m2 for adults and up to 20–25 people / m2 for schoolchildren.

At the suggestion of A.I. Milinsky, the flux density is measured as the ratio of the part of the area of ​​the aisles occupied by people to the total area of ​​the aisles. This value characterizes the degree to which evacuation routes are filled with evacuees. The part of the area of ​​the aisles occupied by people is determined as the sum of the areas of the horizontal projections of each person (Appendix E, table EL). The area of ​​the horizontal projection of one person depends on age, character, clothing and ranges from 0.04 to 0.126 m 2. In each individual case, the projection area of ​​one person can be defined as the area of ​​an ellipse:

(1)

where a- person's width, m; with- its thickness, m

The width of an adult at the shoulders ranges from 0.38 to 0.5 m, and the thickness is from 0.25 to 0.3 m. Bearing in mind the different heights of people and some compressibility of the flow due to clothing, the density may in some cases exceed 1 mm. This density will be called relative, or dimensionless, and denote by D o.

Due to the fact that there are people of different ages, sexes and different configurations in the flow, the data on the flow density represent, to a certain extent, averaged values.

For calculations of forced evacuation, the concept is introduced calculated density of human streams. The estimated density of human flows means the highest density value possible when moving on any part of the evacuation route. The maximum possible density is called the limit. The limiting value is understood to mean such a density value, above which mechanical damage to the human body or asphyxiation is caused.

If necessary, you can go from one density dimension to another. In this case, you can use the following ratios:

Where f is the average size of the projection area of ​​one person, m / person;

a- the width of a person, m.

With massive human flows, the stride length is limited and depends on the flow density. If we take the average stride length of an adult to be 70 cm, and the length of the foot equal to 25 cm, then the linear density at which movement with the indicated stride length is possible will be:

0,7+ 0,25 = 0,95.

In practice, it is believed that a step of 0.7 m in length will remain at a linear density of 0.8. This is due to the fact that in case of mass flows, a person moves his leg between those in front, which contributes to the preservation of the step daina.

Travel speed. Surveys of travel speeds at limiting densities have shown that the minimum speeds on the horizontal sections of the track range from 15 to 17 m / min. The design speed of movement, legalized by the design standards for premises with a massive presence of people, is taken equal to 16 m / min.

On sections of the evacuation route or in buildings where the density of flows during forced movement is known to be less than the limit values, the speed of movement will be correspondingly higher. In this case, when determining the speed of forced movement, one proceeds from the length and frequency of a person's stride. For practical calculations, the speed of movement can be determined by the formula:

(4)

where NS- the number of steps per minute equal to 100.

The speed of movement at the limiting densities on the stairs downwards was 10 m / min, and on the stairs upwards - 8 m / min.

Outputs throughput. The specific throughput of exits is the number of people passing through an exit 1 m wide in 1 minute.

The smallest value of the specific throughput, obtained empirically, at a given density is called the calculated specific throughput. The specific throughput of the outlets depends on the width of the outlets, the density of the traffic and the ratio of the width of the traffic to the width of the outlet.

The norms set the throughput of doors up to 1.5 m wide, equal to 50 people / m-min, and 60 people / m-min with a width of more than 1.5 m (for maximum densities).

Dimensions of emergency exits. In addition to the size of evacuation routes and exits, the norms regulate their design and planning solutions, ensuring the organized and safe movement of people.

The fire hazard of production processes in industrial buildings is characterized by the physicochemical properties of substances formed in production. Production of categories A and B, in which liquids and gases circulate, pose a particular danger in case of fires due to the possibility of rapid spread of combustion and smoke from buildings, therefore the length of the paths for them is the smallest. In production of category B, where solid combustible substances are circulated, the rate of propagation of combustion is less, the evacuation period can be slightly increased, and therefore, the length of the evacuation routes will be longer than for production of categories A and B. In production of categories D and D located in buildings of I and II degrees of fire resistance, the length of escape routes is not limited (to determine the category of a building, see Appendix A).

When standardizing, we proceeded from the fact that the number of evacuation routes, exits and their sizes must simultaneously satisfy four conditions:

1) the greatest actual distance from the possible place of stay of a person along the line of free passages or from the door of the most distant room 1 f to the nearest emergency exit must be less than or equal to the required by the standards 1 tr

(5)

2) the total width of emergency exits and stairs provided by the project, d f must be greater than or equal to the required by the standards

3) the number of emergency exits and stairs, for safety reasons, should, as a rule, be at least two.

4) the width of emergency exits and stairs should not be less or more than the values ​​provided for by the standards.

Typically, in industrial buildings, the length of escape routes is measured from the most distant workplace to the nearest emergency exit. Most often, these distances are normalized within the first stage of evacuation. This indirectly increases the total duration of the evacuation of people from the building as a whole. In multi-storey buildings, the length of escape routes in rooms will be less than in single-storey buildings. This absolutely correct position is given in the norms.

The degree of fire resistance of a building also affects the length of escape routes, since it determines the rate of combustion propagation along structures. In buildings of I and II degrees of fire resistance, the length of the evacuation routes, all other things being equal, will be greater than in buildings of III, IV and V degrees of fire resistance.

The degree of fire resistance of buildings is determined by the minimum limits of fire resistance of building structures and the maximum limits of fire propagation along these structures; when determining the degree of fire resistance, it is necessary to use Appendix B.

The length of escape routes for public and residential buildings is provided as the distance from the doors of the most remote premises to the outside or to the staircase with the exit directly or through the lobby. Usually, when assigning the value of the maximum removal, the purpose of the building and the degree of fire resistance are taken into account. According to SNiP P-L.2-62 "Public buildings", the length of the evacuation routes to the exit to the stairwell is insignificant and meets safety requirements.

1. Calculation of the permissible duration of evacuation in case of fire

In the event of a fire, the danger to humans is high temperatures, a decrease in the oxygen concentration in the indoor air and the possibility of loss of visibility due to smoke from buildings.

The time to reach critical temperatures and oxygen concentrations for humans on a fire is called the critical duration of the fire and is designated .

The critical duration of a fire depends on many variables:

(1.1)

where - air volume in the considered building or room, m 3;

with - specific isobaric heat capacity of gas, kJ / kg-deg;

t Kp – temperature critical for humans, equal to 70 ° С;

t H – initial air temperature, ° С;

– the coefficient characterizing heat loss for heating structures and surrounding objects is taken on average equal to 0.5;

Q – heat of combustion of substances, kJ / kg, (Appendix B);

f - combustion surface area, m 2;

NS- weight burning rate, kg / m 2 -min (Appendix B);

v – linear speed of fire propagation over the surface of combustible substances, m / min (Appendix D).

To determine the critical duration of a fire by temperature in industrial buildings using flammable and combustible liquids, you can use the formula obtained on the basis of the heat balance equation:

The free volume of the room corresponds to the difference between the geometric volume and the volume of equipment or objects inside. If it is impossible to calculate the free volume, it is allowed to take it equal to 80% of the geometric volume.

Specific heat capacity of dry air at atmospheric pressure 760 mm. rt. Art., according to tabular data is 1005 kJ / kg-deg at temperatures from 0 to 60 ° C and 1009 kJ / kg-deg at temperatures from 60 to 120 ° C.

With regard to industrial and civil buildings using solid combustible substances, the critical duration of a fire is determined by the formula:

(1.3)

By reducing the concentration of oxygen in the air of the room, the critical duration of the fire is determined by the formula:

(1.4)

where W02 is the oxygen consumption for the combustion of 1 kg of combustible substances, m / kg, according to the theoretical calculation is 4.76 ogmin.

The linear speed of fire propagation during fires, according to VNIIPO, is 0.33–6.0 m / min, more accurate data for different materials are presented in Appendix D.

The critical duration of a fire for loss of visibility and for each of the gaseous toxic combustion products is longer than the previous ones, therefore, they are not taken into account.

From the values ​​of the critical duration of the fire obtained as a result of calculations, the minimum is selected:

(1.5)

The permissible duration of evacuation is determined by the formulas:

where and – correspondingly permissible duration

evacuation and critical duration of a fire during evacuation, min,

m – the safety factor, depending on the degree of fire protection of the building, its purpose and the properties of combustible substances formed in production or being the subject of the furnishings of the premises or their decoration.

For entertainment enterprises with a grate stage, separated from the auditorium by a fire wall and a fire curtain, with fire retardant treatment of combustible substances on the stage, the presence of stationary and automatic extinguishing means and fire warning devices m = 1,25.

For entertainment enterprises in the absence of a grate stage (cinemas, circuses, etc.) m = 1,25.

For entertainment companies with a stage for concert performances T=1,0.

For spectacular enterprises with a grate stage and in the absence of a fire curtain and automatic extinguishing and fire warning devices T= 0,5.

In industrial buildings with automatic extinguishing and fire warning equipment t = 2,0.

In industrial buildings in the absence of automatic extinguishing means and fire warning t = 1,0.

When placing industrial and other processes in buildings of III degree of fire resistance T= 0,65–0,7.

The critical duration of a fire for the building as a whole is set depending on the time of penetration of combustion products and the possible loss of visibility in the communication rooms located before leaving the building.

Experiments carried out on wood combustion have shown that the time after which a loss of visibility is possible depends on the volume of the premises, the weight rate of burning of substances, the speed of flame propagation over the surface of substances and the completeness of combustion. In most cases, a significant loss of visibility during the combustion of solid combustible substances occurred after temperatures that were critical for humans appeared in the room. The greatest amount of smoke-forming substances occurs in the smoldering phase, which is characteristic of fibrous materials.

When fibrous substances are burned in a loosened state, intense combustion from the surface takes place for 1–2 min, after which smoldering begins with violent smoke formation. When solid wood-based products are burned, smoke formation and the spread of combustion products into adjacent rooms are observed after 5–6 minutes.

Observations have shown that at the beginning of the evacuation, the decisive factor in determining the critical duration of a fire is the effect of heat on the human body or a decrease in oxygen concentration. At the same time, it is taken into account that even a slight smoke, in which satisfactory visibility is still maintained, can have a negative psychological effect on evacuees.

As a result, evaluating the critical duration of a fire to evacuate people from the building as a whole, the following can be established.

In case of fires in civil and industrial buildings, where the main combustible material is cellulosic materials (including wood), the critical duration of the fire can be taken equal to 5–6 minutes.

In case of fires in buildings where fibrous materials circulate in a loosened state, as well as flammable and flammable liquids - from 1.5 to 2 minutes.

In buildings in which the evacuation of people cannot be ensured within the specified time, measures should be taken to create smoke-free escape routes.

In connection with the design of high-rise buildings, the so-called smoke-free stairs began to be widely used. Currently, there are several options for the device smoke-free stairs. The most popular option is with the entrance to the staircase through the so-called air zone. Balconies, loggias and galleries are used as an air zone (Figure 2, a, b).

Figure 2 - Smoke-free stairs: a - entrance to the staircase through the balcony; b - entrance to the staircase through the gallery.

2. Calculation of the evacuation time

The duration of the evacuation of people before leaving the building is determined by the length of the escape routes and the throughput of doors and stairs. The calculation is carried out for the conditions that on the evacuation routes the flux densities are uniform and reach maximum values.

According to GOST 12.1.004-91 (Appendix 2, p. 2.4), the total time of evacuation of people is the sum of the interval "time from the occurrence

fire before the start of evacuation of people ", tn e, and the estimated time of evacuation, t p, which is the sum of the time of movement of the human flow in individual sections (t,) its route from the location of people at the time of the beginning of the evacuation to the evacuation exits from the premises, from the floor, from the building.

The need to take into account the time of the beginning of the evacuation for the first time in our country was established by GOST 12.1.004–91. Studies carried out in various countries have shown that when receiving a signal about a fire, a person will investigate the situation, notify about the fire, try to fight the fire, collect things, provide assistance, etc. The average value of the delay time for the start of evacuation (in the presence of a warning system) can be low, but it can also reach relatively high values. For example, the value of 8.6 microns was recorded during a training evacuation in a residential building, 25.6 minutes in the building of the World Trade Center during a fire in 1993.

In view of the fact that the duration of this stage significantly affects the total evacuation time, it is very important to know what factors determine its value (it should be borne in mind that most of these factors will also affect throughout the entire evacuation process). Based on the existing work in this area, the following can be distinguished:

Human condition: persistent factors (limitation of the sense organs, physical limitations, temporary factors (sleep / wakefulness), fatigue, stress, as well as a state of intoxication);

Notification system;

Staff actions;

Social and family ties of a person;

Firefighting training and education;

Building type.

The delay time for the start of the evacuation is taken according to Appendix D.

Estimated time of evacuation of people (t P) should be defined as the sum of the time of movement of the flow of people along individual sections of the path t f:

......................................................... (2.1)

where - time delay of the beginning of evacuation;

t 1 - time of movement of the flow of people in the first section, min;

t 2 , t 3 ,.......... t i - time of movement of the flow of people on each of the following sections of the path after the first, min.

When calculating, the entire path of movement of the human flow is divided into sections (passage, corridor, doorway, staircase, vestibule) with length /, and width bj. The starting areas are the aisles between workstations, equipment, rows of chairs, etc.

When determining the estimated time, the length and width of each section of the escape route are taken according to the project. The length of the path along the flights of stairs, as well as along the ramps, is measured along the length of the flight. The length of the path in the doorway is taken to be zero. An opening located in a wall with a thickness of more than 0.7 m, as well as a vestibule, should be considered an independent section of a horizontal path with a finite length.

Time of movement of the flow of people along the first section of the path (t;), min, calculated by the formula:

(2.2)

where – length of the first track section, m;

- the value of the speed of movement of the flow of people along the horizontal path in the first section, is determined depending on the relative density D, m 2 / m 2.

The density of the flow of people (D) on the first section of the path, m / m, is calculated by the formula:

where – the number of people in the first section, people;

f is the average area of ​​the horizontal projection of a person, taken according to Table E. 1 of Appendix E, m 2 / person;

and – length and width of the first section of the track, m.

The speed V / of the movement of the human flow on the sections of the path following the first is taken according to Table E.2 of Appendix E, depending on the value of the intensity of movement of the traffic in each of these sections of the path, which is calculated for all sections of the path, including for the door openings, according to the formula:

where , - the width of the considered i-th and the preceding section of the track, m;

, – values ​​of the traffic intensity of the human flow along the considered i-th and previous sections of the path, m / min.

If the value , determined by formula (2.4) is less than or equal to the value q max, then the time of movement along the section of the path () per minute: in this case, the values q max, m / min, should be taken according to table 2.1.

Table 2.1 - Traffic intensity of people

If the value q h defined by formula (2.4) is greater than q max, then the width bj of this section of the path should be increased by such a value at which the condition is met:

If it is impossible to satisfy condition (2.6), the intensity and speed of movement of the human flow along the section of the path i determined according to Table E.2 of Appendix E with the value D = 0.9 or more. In this case, the time delay in the movement of people due to the formed congestion should be taken into account.

When merging at the beginning of the site i two or more human streams (Figure 3) traffic intensity ( }, m / min, calculated by the formula:

(2.7)

- traffic intensity of human streams merging at the beginning of the section /, m / min;

i – width of the path sections of the confluence, m;

– width of the track section under consideration, m

If the value defined by formula (2.7) is greater than q max, then the width of this section of the track should be increased by such an amount that condition (2.6) is met. In this case, the time of movement on the site i is determined by formula (2.5).

The intensity of traffic in a doorway with a width of less than 1.6 m is determined by the formula:

Where b is the width of the opening.

The time of movement through the opening is defined as the quotient of dividing the number of people in the stream by the throughput of the opening:

Figure 3 - Merging human streams

3. Calculation procedure

· Select the minimum from the calculated critical fire durations and use it to calculate the permissible evacuation duration according to formula (1.6).

· Determine the estimated time of evacuation of people in case of fire, using the formula (2.1).

· Compare the estimated and permissible evacuation time, draw conclusions.

4. Calculation example

It is necessary to determine the time of evacuation from the office of employees of the "Obus" enterprise in the event of a fire in the building. The administrative building is panel type, not equipped with an automatic alarm and fire warning system. The building is two-storey, has dimensions in plan of 12x32 m, in its corridors 3 m wide there are schemes for evacuating people in case of fire. An office with a volume of 126 m 3 is located on the second floor in the immediate vicinity of the staircase leading to the first floor. The stairwells are 1.5 m wide and 10 m long. 7 people work in the office. A total of 98 people work on the floor. 76 people work on the ground floor. The evacuation scheme from the building is shown in Figure 4.

Figure 4 - Scheme of evacuation of employees of the enterprise "Obus": 1,2,3,4 - stages of evacuation

4.1 Calculation of the evacuation time

4.1.2. The critical duration of a fire in terms of temperature is calculated using the formula (1.3), taking into account the furniture in the room:

4.1.3 The critical duration of a fire in terms of oxygen concentration is calculated using the formula (1.4):

4.1.4 Minimum fire duration by temperature
is 5.05 minutes. Allowable evacuation time for a given
premises:

4.1.5 The delay time for the start of evacuation is taken as 4.1 minutes according to Table D. 1 of Appendix D, taking into account the fact that the building does not have an automatic alarm and fire warning system.

4.1.6 To determine the time of movement of people in the first section, taking into account the overall dimensions of the office 6x7 m, the traffic density of the human flow in the first section is determined using the formula (2.3):

.

According to table E.2 of Appendix E, the speed of movement is 100 m / min, the intensity of movement is 1 m / min, i.e. time of movement along the first section:

4.1.7 The length of the doorway is taken to be zero. The greatest possible traffic intensity in the opening under normal conditions is g mffic = 19.6 m / min, the traffic intensity in the opening with a width of 1.1 m is calculated by the formula (2.8):

q d = 2,5 + 3,75 b= 2.5 + 3.75 1.1 = 6.62 m / min,

q d therefore, movement through the opening is unimpeded.

The time of movement in the opening is determined by the formula (2.9):

4.1.8. Since 98 people work on the second floor, the density of the people flow on the second floor will be:

According to table E2 of Appendix E, the speed of movement is 80 m / min, the intensity of movement is 8 m / min, i.e. time of movement along the second section (from the corridor to the stairs):

4.1.9 To determine the speed of movement on the stairs, the traffic intensity in the third section is calculated according to the formulas (2.4):

,

This shows that the speed of the flow of people on the stairs is reduced to 40 m / min. Time of moving down the stairs (3rd section):

4.1.10 When moving to the first floor, mixing with the flow of people moving along the first floor occurs. Traffic density for the first floor:

the traffic intensity will be about 8 m / min.

4.1.11. When moving to the 4th section, there is a merger of human streams, therefore, the intensity of movement is determined by the formula (2.7):

According to table E.2 of Appendix E, the speed of movement is 40 m / min, therefore the speed of movement along the corridor of the first floor:

4.1.12 The tambour when entering the street has a length of 5 meters, on this section the maximum density of the human flow is formed, therefore, according to the application, the speed drops to 15 m / min, and the time of movement along the tambour will be:

4.1.13 At the maximum density of the human flow, the intensity of traffic through the doorway to the street with a width of more than 1.6 m - 8.5 m / min, the time of movement through it:

4.1.13 Estimated time of evacuation is calculated by the formula (2.1):

4.1.14 Thus, the estimated time of evacuation from the offices of the Obus enterprise is longer than the permissible one. Therefore, the building in which the enterprise is located must be equipped with a fire warning system, automatic signaling devices.

List of sources used

1 Labor protection in construction: Textbook. for universities / N.D. Zolotnitsky [and others]. - M .: Higher school, 1969 .-- 472 p.

2 Labor safety in construction (Engineering calculations for the discipline "Life Safety"): Textbook / D.V. Koptev [and others]. - M .: Publishing house ASV, 2003 .-- 352 p.

3 Fetisov, P.A. Fire safety handbook. - M .: Energoizdat, 1984 .-- 262 p.

4 Table of physical quantities: Handbook. / I.K. Kikoin [and others]

5 Schreiber , D. Fire extinguishing agents. Physicochemical processes during combustion and extinguishing. Per. with him. - M .: Stroyizdat, 1975 .-- 240 p.

6 GOST 12.1.004–91. SSBT. Fire safety. General requirements. - Introduce. from 01.07.1992. - M .: Publishing house of standards, 1992.-78 p.

7 Dmitrichenko A.S. A new approach to the calculation of forced evacuation of people during fires / A.S. Dmitrichenko, S.A. Sobolevsky, S.A. Tatarnikov // Fire and explosion safety, No. 6. - 2002. - S. 25–32.

Appendix A

Appendix B

Table B.1 - Degree of fire resistance for various buildings

Appendix B

Table B.1 - Average burnup rate and heat of combustion of substances and materials

Appendix D

Table D.1 - Linear speed of flame propagation on the surface of materials

Appendix D

Table D. 1 - Delay time for the start of evacuation

Appendix E

Table E.1 - Human projection area

Table E.2 - Dependence of the speed and intensity of traffic on the density of the human flow