Fire safety of building materials. Building materials and their fire hazard properties. Parts of buildings and structures and their fire resistance 7 highly flammable group of combustible building materials

GOST 30244-94

INTERSTATE STANDARD

CONSTRUCTION MATERIALS

FLAMMABILITY TEST METHODS

INTERSTATE SCIENTIFIC AND TECHNICAL COMMISSION
FOR STANDARDIZATION AND TECHNICAL REGULATION
IN CONSTRUCTION (MNTKS)

Moscow

Foreword

1 DEVELOPED by the State Central Scientific Research and Design Experimental Institute for Complex Problems of Building Structures and Structures named after V.A. Kucherenko (TsNIISK named after Kucherenko) and the Center for Fire Research and Thermal Protection in Construction TsNIISK (TsPITZS TsNIISK) of the Russian Federation

INTRODUCED by the Ministry of Construction of Russia

2 ADOPTED by the Interstate Scientific and Technical Commission for Standardization and Technical Regulation in Construction (ISTC) on November 10, 1993

3 Clause 6 of this standard is the authentic text of ISO 1182-80 Fire tests - Building mattrifls - Non-combustibility test Fire tests. - Construction Materials. - Test for incombustibility "(Third edition 1990-12-01).

4 PUT INTO EFFECT from January 1, 1996 as a state standard of the Russian Federation by the Decree of the Ministry of Construction of Russia dated August 4, 1995 No. 18-79

5 REPLACE ST SEV 382-76, ST SEV 2437-80

INTERSTATE STANDARD

CONSTRUCTION MATERIALS

Flammability test methods

Building materials.

Methods for combustibility test

Date of introduction 1996-01-01

1 AREA OF USE

This standard establishes methods for testing building materials for combustibility and their classification according to combustibility groups.

The standard does not apply to varnishes, paints, and other building materials in the form of solutions, powders and granules.

2 REFERENCES

6.3.5 The tube furnace is installed in the center of a casing filled with insulating material (outer diameter 200 mm, height 150 mm, wall thickness 10 mm). The upper and lower parts of the casing are limited by plates having recesses on the inside for fixing the ends of the tube furnace. The space between the tube furnace and the walls of the casing is filled with powdered magnesium oxide with a density of (140 ± 20) kg / m 3.

6.3.6 The bottom of the tube furnace is connected to a 500 mm long cone-shaped air flow stabilizer. The inner diameter of the stabilizer should be (75 ± 1) mm at the top, (10 ± 0.5) mm at the bottom. The stabilizer is made of 1 mm thick sheet steel. The inner surface of the stabilizer must be polished. The seam between the stabilizer and the oven should be tightly fitted to ensure a tight seal and carefully finished to remove any roughness. The upper half of the stabilizer is insulated from the outside with a layer of mineral fiber 25 mm thick [thermal conductivity (0.04 ± 0.01) W / (m × K) at 20 ° WITH].

6.3.7 The upper part of the furnace is equipped with a protective screen made of the same material as the stabilizer cone. The height of the screen should be 50 mm, the inner diameter (75 ± 1) mm. The inner surface of the screen and the connecting seam with the oven are carefully processed until a smooth surface is obtained. The outer part is insulated with a layer of mineral fiber 25 mm thick [thermal conductivity (0.04 ± 0.01) W / (m × K) at 20 ° C].

6.3.8 A block consisting of a furnace, a cone-shaped stabilizer and a protective screen is mounted on a frame equipped with a base and a screen to protect the lower part of the cone-shaped stabilizer from directed air flows. The height of the protective shield is approximately 550 mm, the distance from the bottom of the tapered stabilizer to the base of the bed is approximately 250 mm.

6.3.9 To observe the flame combustion of the sample above the furnace at a distance of 1 m at an angle of 30 ° C, a mirror with an area of ​​300 mm 2 is installed.

6.3.10 The installation should be placed so that directed air currents or intense sunlight, as well as other types of light radiation, do not interfere with the observation of the flame combustion of the sample in the furnace.

6.3.18 Temperature registration is carried out throughout the experiment using appropriate instruments.

A schematic diagram of the installation with measuring instruments is shown on.

6.4 Preparing the installation for testing

6.4.1 Remove the sample holder from the oven. The oven thermocouple must be installed in accordance with.

Note- The operations described in - should be carried out when a new installation is put into operation or when replacing a chimney, heating element, thermal insulation, power supply.

6.5Testing

6.5.1 Remove the sample holder from the furnace, check the installation of the furnace thermocouple, turn on the power supply.

6.5.2 Stabilize the oven in accordance with.

6.5.3 Place the sample in the holder, place the thermocouples in the center and on the surface of the sample in accordance with -.

6.5.4 Insert the sample holder into the oven and position it according to. The duration of the operation should be no more than 5 seconds.

6.5.5 Start the stopwatch immediately after introducing the sample into the oven. During the test, record the readings of thermocouples in the oven, in the center and on the surface of the sample.

6.5.6 The test duration is generally 30 min. The test is stopped after 30 minutes, provided that the temperature balance has been reached by this time. The temperature balance is considered achieved if the readings of each of the three thermocouples change by no more than 2 ° From in 10 min. In this case, the final thermocouples are fixed in the furnace, in the center and on the surface of the sample.

If, after 30 minutes, the temperature balance is not achieved for at least one of the three thermocouples, the test is continued, checking the temperature balance at intervals of 5 minutes.

6.5.7 When the temperature balance is reached for all three thermocouples, the test is stopped and its duration recorded.

6.5.8 Remove the sample holder from the oven, cool the sample in a desiccator and weigh.

Residues (carbonization products, ash, etc.) that have fallen off the sample during or after testing are collected, weighed and included in the weight of the sample after testing.

Photos of samples after testing;

Conclusion on the test results indicating what type of material the material belongs to: combustible or non-combustible;

The term of the conclusion.

7 METHOD OF TESTING COMBUSTIBLE BUILDING MATERIALS TO DETERMINE THEIR FLAMMABILITY GROUPS

Method II

7.1 Application area

The method is used for all homogeneous and layered combustible building materials, including those used as finishing and facing, as well as paint and varnish coatings.

7.2 Samples for testing

7.3.2 The design of the walls of the combustion chamber shall ensure the stability of the temperature conditions of the tests established by this standard. For this purpose, it is recommended to use the following materials:

For the inner and outer surfaces of the walls - sheet steel 1.5 mm thick;

For the heat-insulating layer - mineral wool slabs [density 100 kg / m 3, thermal conductivity 0.1 W / (m × K), thickness 40 mm].

7.3.3 Install the sample holder, ignition source, diaphragm in the combustion chamber. The front wall of the combustion chamber is equipped with a door with glazed openings. A hole with a plug for introducing thermocouples should be provided in the center of the side wall of the chamber.

7.3.4 The specimen holder consists of four rectangular frames located around the perimeter of the ignition source (), and must ensure the indicated position of the specimen relative to the ignition source, the stability of the position of each of the four specimens until the end of the test. The sample holder should be mounted on a support frame that allows it to move freely in the horizontal plane. The specimen holder and fixing parts should not overlap the sides of the exposed surface by more than 5 mm.

7.3.5 The ignition source is a gas burner made up of four separate segments. Mixing of gas with air is carried out through the holes located on the gas supply pipes at the entrance to the segment. The location of the burner segments relative to the sample and its schematic diagram are shown in.

7.3.6 The air supply system consists of a fan, a rotameter and a diaphragm, and must ensure that an air flow uniformly distributed over its cross section is supplied to the lower part of the combustion chamber in an amount of (10 ± 1.0) m 3 / min with a temperature of at least (20 ± 2) ° C.

7.3.7 The diaphragm is made of a perforated steel sheet 1.5 mm thick with holes (20 ± 0.2) mm and (25 ± 0.2) mm in diameter and a metal mesh of wire located above it at a distance of (10 ± 2) mm with a diameter of no more than 1.2 mm with a mesh size of no more than 1.5 ´ 1.5 mm. The distance between the diaphragm and the upper plane of the burner must be at least 250 mm.

7.3.9 The ventilation system for the removal of combustion products consists of an umbrella installed above the flue pipe, an air duct and a ventilation pump.

7.3.10 To measure the temperature during testing, use thermocouples with a diameter of not more than 1.5 mm and appropriate recording devices.

7.4 Test preparation

7.4.1 Preparation for the test consists in carrying out a calibration in order to establish the gas flow rate (l / min), which ensures the temperature regime of the test in the combustion chamber, established by this standard (table 3).

Insert the holder with the sample into the combustion chamber, turn on the measuring instruments, air supply, exhaust ventilation, ignition source, close the door, record the thermocouple readings 10 minutes after turning on the ignition source.

If the temperature regime in the combustion chamber does not correspond to the requirements, repeat the calibration at other gas flow rates.

The gas flow rate set during the calibration should be used for testing until the next calibration.

7.5 Testing

7.5.1 Three tests should be performed for each material. Each of the three tests involves the simultaneous testing of four samples of material.

7.5.2 Check the flue gas temperature measuring system by switching on the measuring devices and air supply. This operation is carried out with the door of the combustion chamber closed and the ignition source inoperative. The deviation of the readings of each of the four thermocouples from their arithmetic mean value should be no more than 5 ° WITH.

7.5.3 Weigh four samples, place in the holder, and insert it into the combustion chamber.

7.5.4 Switch on instrumentation, air supply, exhaust ventilation, ignition source, close the chamber door.

7.5.5 The duration of exposure of the sample to the flame from the ignition source shall be 10 min. After 10 minutes, the ignition source is turned off. In the presence of a flame or signs of smoldering, the duration of self-burning (smoldering) is recorded. The test is considered complete when the samples have cooled to ambient temperature.

7.5.6 After the end of the test, turn off the air supply, exhaust ventilation, measuring instruments, remove the samples from the combustion chamber.

7.5.7 For each test, the following parameters are determined:

Flue gas temperature;

Duration of self-burning and (or) smoldering;

The length of the damage to the sample;

Sample weight before and after testing.

7.5.8 During the test, the temperature of the flue gases is recorded at least twice a minute according to the readings of all four thermocouples installed in the gas outlet pipe, and the duration of self-combustion of the samples (in the presence of a flame or signs of smoldering) is recorded.

7.5.9 The following observations are also recorded during the test:

Time to reach the maximum flue gas temperature;

Flame transfer to the ends and unheated surface of the samples;

Burn-through of samples;

Burning melt formation;

Appearance of the samples after testing: sedimentation of soot, discoloration, melting, sintering, shrinkage, swelling, warping, cracking, etc .;

The time until the flame spreads along the entire length of the sample;

Duration of burning along the entire length of the sample.

7.6 Processing of test results

7.6.1 After the end of the test, measure the length of the sections of the undamaged part of the samples (by) and determine the residual mass t to samples.

The part of the sample that is not burnt or charred, either on the surface or inside, is considered intact. Soot deposition, discoloration of the sample, local chips, sintering, melting, swelling, shrinkage, warping, change in surface roughness are not considered damage.

The measurement result is rounded to the nearest 1 cm.

The undamaged portion of the samples remaining on the holder is weighed. The weighing accuracy should be at least 1% of the initial weight of the sample.

7.6.2 Processing the results of one test (four samples)

7.6.2.1 Flue gas temperature T i is taken equal to the arithmetic mean of the simultaneously recorded maximum temperature readings of all four thermocouples installed in the gas outlet pipe.

7.6.2.2 The damage length of one specimen is determined by the difference between the nominal length before testing (by) and the arithmetic mean length of the undamaged part of the specimen, determined from the lengths of its segments, measured in accordance with

Measured line lengths should be rounded to the nearest 1 cm.

7.6.2.3 The damage length of the test pieces is determined as the arithmetic mean of the damage lengths of each of the four test pieces.

7.6.2.4 The damage by mass of each sample is determined by the difference between the mass of the sample before testing and its residual mass after testing.

7.6.2.5 Damage by mass of samples is determined by the arithmetic mean of this damage for the four tested samples.

7.7 Test report

7.7.1 The following data shall be given in the test report:

Test date;

Name of the laboratory conducting the test;

Customer name;

Material name;

The code of the technical documentation for the material;

Description of the material indicating the composition, manufacturing method and other characteristics;

The name of each material that is an integral part of the laminated material, indicating the thickness of the layer;

A method for making a sample with an indication of the base material and the method of fastening;

Additional observations during the test;

Characteristics of the exposed surface;

Test results (parameters of flammability according to);

Photo of the sample after testing;

Conclusion based on the test results on the flammability group of the material.

For materials tested according to and, indicate the flammability groups for all cases established by these paragraphs;

The term of the conclusion.

APPENDIX A

(required)

INSTALLATION FOR TESTING BUILDING MATERIALS FOR NON-FLAMMABILITY (method - thermocouple in the center of the sample;T s - a thermocouple on the sample surface; 1 - stainless steel tube; 2 - mesh (mesh size 0.9 mm, wire diameter 0.4 mm)

Figure A3 - Sample holder

1 - wooden handle; 2 - weld

T f- furnace thermocouple; T C - a thermocouple in the center of the sample;T s - a thermocouple on the sample surface; 1 - furnace wall; 2 - mid-altitude of the constant temperature zone; 3 - thermocouples in a protective casing; 4 - contact of thermocouples with material

Figure A5 - Relative position of furnace, sample and thermocouples

Flammability group materials is determined in accordance with GOST 30244-94 "Building materials. Methods of testing for flammability", which corresponds to the International standard ISO 1182-80 "Fire tests - Building materials - Non-combastibility test". Materials, depending on the values ​​of the flammability parameters determined according to this GOST, are divided into non-combustible (NG) and combustible (G).

Materials include to non-flammable with the following values ​​of flammability parameters:

1. the temperature rise in the furnace is no more than 50 ° С;
2. weight loss of the sample is not more than 50%;
3. duration of stable flame combustion no more than 10 sec.

Materials that do not meet at least one of the specified parameter values ​​are classified as fuels.

Combustible materials, depending on the values ​​of the flammability parameters, are divided into four flammability groups in accordance with Table 1.

Table 1. Flammability groups of materials.

Flammability group of materials determined according to GOST 30402-96 "Building materials. Flammability test method", which corresponds to the international standard ISO 5657-86.

In this test, the surface of the specimen is exposed to a radiant heat flux and flame from an ignition source. At the same time, the surface density of the heat flux (PPTP) is measured, that is, the magnitude of the radiant heat flux affecting the unit surface area of ​​the sample. Ultimately, the Critical surface heat flux density (KPTPP) is determined - the minimum value of the surface heat flux density (PPTP), at which a stable flame combustion of the sample occurs after exposure to the flame.

Depending on the values ​​of KPPTP, materials are divided into three groups of flammability, indicated in table 2.

Table 2. Flammability groups of materials.

For the classification of materials by smoke generating abilities use the value of the smoke production coefficient, which is determined in accordance with GOST 12.1.044.

Smoke production coefficient is an indicator characterizing the optical density of smoke generated during flame combustion or thermo-oxidative destruction (smoldering) of a certain amount of a solid (material) under special test conditions.

Depending on the value of the relative density of smoke, materials are divided into three groups:
D1- with low smoke-generating ability - smoke production coefficient up to 50 m² / kg inclusive;
D 2- with moderate smoke-generating ability - smoke production coefficient from 50 to 500 m² / kg inclusive;
D3- with high smoke-generating ability - smoke production coefficient over 500 m² / kg.

Toxicity group combustion products of building materials is determined in accordance with GOST 12.1.044. The combustion products of the material sample are sent to a special chamber where the experimental animals (mice) are. Depending on the state of the experimental animals after exposure to combustion products (including death), materials are divided into four groups:
T1- slightly dangerous;
T2- moderately dangerous;
T3- highly dangerous;
T4- extremely dangerous.

Classification of building materials

By origin and purpose

By origin, building materials can be divided into two groups: natural and artificial.

Natural refers to such materials that occur in nature in finished form and can be used in construction without significant processing.

Artificial they call building materials that do not occur in nature, but are manufactured using various technological processes.

By designation, building materials are divided into the following groups:

Materials intended for the construction of walls (brick, wood, metals, concrete, reinforced concrete);

Binder materials (cement, lime, gypsum) used to obtain non-fired products, masonry and plaster;

Thermal insulation materials (foam and aerated concrete, felt, mineral wool, polystyrene, etc.);

Finishing and facing materials (rocks, ceramic tiles, various types of plastics, linoleum, etc.);

Roofing and waterproofing materials (roofing steel, tiles, asbestos-cement sheets, slate, roofing felt, roofing material, isol, brizol, poroizol, etc.)

NON-FLAMMABLE BUILDING MATERIALS

Natural stone materials. Building materials obtained from rocks by using only mechanical processing (crushing, sawing, splitting, grinding, etc.) are called natural stone materials. They are used for the construction of walls, flooring, staircases and building foundations, cladding of various structures. In addition, rocks are used in the production of artificial stone materials (glass, ceramics, thermal insulation materials), as well as as raw materials for the production of binders: gypsum, lime, cement.

The effect of high temperatures on natural stone materials. All natural stone materials used in construction are non-combustible, however, under the influence of high temperatures in stone materials, various processes occur, leading to a decrease in strength and destruction.

The minerals included in stone materials have different coefficients of thermal expansion, which can lead to the appearance of internal stresses in the stone during heating and the appearance of defects in its internal structure.

The material undergoes a modification transformation of the crystal lattice structure associated with an abrupt increase in volume. This process leads to cracking of the monolith and a drop in the strength of the stone due to large temperature deformations resulting from sudden cooling.

It should be emphasized that all stone materials irreversibly lose their properties under the influence of high temperatures.

Ceramic products. Since all ceramic materials and products in the process of their production are fired at high temperatures, the repeated action of high temperatures under fire conditions does not significantly affect their physical and mechanical properties if these temperatures do not reach the softening (melting) temperatures of the materials. Porous ceramic materials (ordinary clay brick, etc.), obtained by firing, which is not brought to sintering, can succumb to moderately high temperatures, as a result of which some shrinkage of structures made of them is possible. The impact of high temperatures in a fire on dense ceramic products, which are fired at temperatures of about 1300 ° C, practically does not have any harmful effect, since the temperature on a fire does not exceed the firing temperature.

Red clay brick is the best material for fire walls.

Metals. In construction, metals are widely used for the construction of frames for industrial and civil buildings in the form of rolled steel profiles. A large amount of steel is used to make reinforcement for reinforced concrete. Steel and cast iron pipes, roofing steel are used. In recent years, lightweight building structures made of aluminum alloys have found more and more widespread use.

Behavior of steels in case of fire. One of the most characteristic features of all metals is the ability to soften when heated and restore their physical and mechanical properties after cooling. In a fire, metal structures very quickly warm up, lose strength, deform and collapse.

Reinforcing steels will behave worse in fire conditions (see the "References" section), which are obtained by additional hardening by means of heat treatment or cold broaching (work hardening). The reason for this phenomenon lies in the fact that additional strength of these steels is obtained due to the distortion of the crystal lattice, and under the influence of heating, the crystal lattice returns to an equilibrium state and the increase in strength is lost.

Aluminum alloys. The disadvantage of aluminum alloys is a high coefficient of thermal expansion (2-3 times higher than that of steel). When heated, there is also a sharp decrease in their physical and mechanical parameters. The tensile strength and yield strength of aluminum alloys used in construction are approximately halved at a temperature of 235-325 ° C. Under fire conditions, the temperature in the room volume can reach these values ​​in less than one minute.

Materials and products based on mineral melts and products from glass melts. This group includes: glass materials, products from slag and stone casting, sitalls and slag glass, sheet window and display glass, patterned, reinforced, sun- and heat-shielding, facing glass, glass profiles, double-glazed windows, glass carpet-mosaic tiles, glass blocks, etc. ...

Behavior of materials and products from mineral melts at high temperatures. Materials and products made from mineral melts are non-flammable and cannot contribute to the development of a fire. Exceptions are materials based on mineral fibers containing a certain amount of organic binder, such as thermal insulation mineral slabs, silica slabs, slabs and roll mats made of basalt fiber. The flammability of such materials depends on the amount of binder introduced. In this case, its fire hazard will be determined mainly by the properties and the amount of polymer in the composition.

Window glass does not withstand prolonged thermal loads in a fire, but with slow heating it may not collapse for a long time. Glass breakage in skylights begins almost immediately after the flame begins to touch its surface.

Constructions made of tiles, stones, blocks, obtained on the basis of mineral melts, have a significantly higher fire resistance than sheet glass, since, even when cracked, they continue to bear the load and remain sufficiently impervious to combustion products. Porous materials from mineral melts retain their structure almost up to the melting temperature (for foam glass, for example, this temperature is about 850 ° C) and for a long time perform heat-shielding functions. Since porous materials have a very low coefficient of thermal conductivity, even at the moment when the side facing the fire melts, deeper layers can perform heat-shielding functions.

FLAMMABLE BUILDING MATERIALS

Wood... When wood is heated to 110 ° C, moisture is removed from it, and gaseous products of thermal destruction (decomposition) begin to evolve. When heated to 150 ° C, the heated wood surface turns yellow, the amount of emitted volatile substances increases. At 150-250 ° C, the wood becomes brown due to charring, and at 250-300 ° C, the wood decomposition products are ignited. The self-ignition temperature of wood is in the range of 350-450 ° C.

Thus, the process of thermal decomposition of wood proceeds in two phases: the first phase - decomposition - is observed when heated to 250 ° C (to the ignition temperature) and proceeds with heat absorption, the second, the combustion process itself, proceeds with the release of heat. The second phase, in turn, is subdivided into two periods: combustion of gases formed during the thermal decomposition of wood (flame phase of combustion), and combustion of the resulting charcoal (smoldering phase).

Bituminous and tar materials. Building materials, which include bitumen or tar, are called bituminous or tar.

Ruberoid and tarpaulin roofs can ignite even from low-power sources of fire, such as sparks, and continue to burn on their own, emitting a large amount of thick black smoke. When burning, bitumen and tar soften and spread, which significantly complicates the situation on a fire.

The most common and effective way to reduce the flammability of roofs made of bituminous and tar materials is to sprinkle them with sand, backfill with a continuous layer of gravel or slag, and cover with any non-combustible tiles. Some fire-retardant effect is provided by coating roll materials with foil - such coatings do not ignite when exposed to sparks.

It should be borne in mind that rolled materials made with bitumen and tar are prone to spontaneous combustion when rolled up. This circumstance must be taken into account when storing such materials.

Polymeric building materials. Polymeric building materials (PSM) are classified according to various criteria: the type of polymer (polyvinyl chloride, polyethylene, phenol-formaldehyde, etc.), production technologies (extrusion, casting, roll-calender, etc.), purpose in construction (structural, finishing, floor materials , heat and sound insulation materials, pipes, sanitary-technical and molded products, mastics and adhesives). All polymer building materials are highly flammable, smoke-generating and toxic.

The technical code of established practice establishes the fire-technical classification of building materials, products, structures, buildings and their elements. This normative act regulates the classification of materials, products and structures for fire hazard, depending on the fire-technical characteristics, as well as the methods of determination.

The fire hazard of building materials is determined by the following fire-technical characteristics or their combination:

Flammability;

Flammability;

Spread of flame over the surface;

Toxicity of combustion products;

Smoke-generating ability.

Building materials, depending on the values ​​of the flammability parameters determined according to GOST 30244, are subdivided into non-combustible
and flammable. For building materials containing only inorganic (non-combustible) components, the characteristic "flammability"
not defined.

Combustible building materials are classified according to:

1. Values ​​of flammability parameters, determined according to GOST 30244 into flammability groups:

G1, slightly flammable;

G2, moderately flammable;

G3, normally flammable;

G4, highly flammable.

2. The values ​​of the critical surface density of the heat flux in accordance with GOST 30402 into flammability groups:

B1, hardly flammable;

B2, moderately flammable;

B3, highly flammable.

3. In The values ​​of the critical surface density of the heat flux in accordance with GOST 30444 for groups by flame propagation:

RP1, not distributing;

RP2, weakly spreading;

WP3, moderately spreading;

WP4, highly spreading.

4. Lethal effect of gaseous combustion products from the mass of material per unit volume of the exposure chamber
according to GOST 12.1.044 into groups according to the toxicity of combustion products:

T1, low hazard;

T2, moderately dangerous;

T3, highly dangerous;

T4, extremely dangerous.

4. Values ​​of the smoke production coefficient in accordance with GOST 12.1.044 into groups by smoke-generating ability:

D1, with low smoke-generating ability;

D2, with moderate smoke-generating ability;

D3, with high smoke-generating ability.

In accordance with the federal law of July 22, 2008 N 123-FZ, the fire-technical classification of construction products - buildings, structures and building materials - is based on their assessment:

· by fire hazard, i.e. properties contributing to the occurrence of hazardous factors of fire and its development;

· fire resistance , i.e. the properties of resistance to fire and the spread of its hazardous factors.

Fire hazard analysis consists in determining the amount and fire hazardous properties of substances and materials, the conditions of their ignition, the characteristics of building structures, buildings and structures, the possibility of fire spread and the assessment of the danger to people, etc.

Construction Materials characterized by only fire hazard. It is determined by the following characteristics: flammability, flammability, flame spread over the surface, toxicity, smoke-generating ability.

Fire hazard properties are primarily associated with the flammability of substances and materials, i.e. with their ability to burn, which, in turn, is characterized by the behavior of the sample of the material in the flame of the heat source and after its removal. In accordance with GOST 30244-94, solid materials are divided into non-combustible (NG) and combustible (G).

Non-combustible substances and materials are not capable of self-combustion in air, and combustible ones are capable of spontaneously igniting, igniting from an ignition source and supporting the development of combustion.

Combustible materials, depending on the temperature of the flue gases, the intensity of combustion and the duration of independent combustion, are subdivided in turn into four groups of flammability:

· D1 (slightly flammable);

· G2 (moderately flammable);

· G3 (normally flammable);

· G4 (highly flammable).

Materials of the G1 group are incapable of burning independently, they burn only in the presence of more flammable materials such as, for example, materials of the G4 group, which burn well on their own until they completely burn out. Group G4 includes materials of increased fire hazard - polyurethane foams, polystyrene foams and similar organic materials with low density, intensively developing combustion and capable of forming burning melts.

The flammability of building materials is determined by the ignition time at given values ​​of the surface density of the heat flux. Flammability materials are divided (GOST 30402-96) into three groups:

· IN 1 (hardly flammable);

· IN 2 (moderately flammable);

· AT 3 (flammable).

Flame propagation is estimated from the length of the flame propagation over the surface and the critical surface density of the heat flux, as well as the ignition time of the sample. Combustible building materials on the spread of flame over the surface are subdivided (GOST R 51032-97) into four groups:

· RP1 (non-proliferating);

· RP2 (weakly spreading);

· RP3 (moderately spreading);

· RP4 (highly propagating).

Smoke production coefficient is an indicator characterizing the optical density of smoke formed during flame combustion or thermal oxidative destruction (smoldering) of a certain amount of solid matter (material). Combustible building materials by smoke generating ability are subdivided (GOST 12.1.044) into three groups:

· D1 (with low smoke-generating ability);

· D 2 (with moderate smoke-generating ability);

· DZ (with high smoke-generating ability).

The indicator of toxicity of combustion products is the ratio of the amount of material to a unit volume of a closed space in which gaseous products formed during the combustion of the material cause the death of 50% of the experimental animals. Combustible building materials toxicity combustion products are divided according to GOST 12.1.044 into four groups:

· T1 (low-hazard);

· T2 (moderately dangerous);

· TK (highly hazardous);

· T4 (extremely dangerous).

All the above fire hazard properties affect the comprehensive assessment of the material - its fire hazard class

Building construction are characterized by fire resistance and fire hazard. The main characteristic of a building structure is the ability to maintain load-bearing and / or enclosing functions in a fire, which is assessed fire resistance limit.

Fire resistance limit- this is the time during which a building structure resists the effects of fire or a high fire temperature until one or several successive fire resistance limit states occur, taking into account the functional purpose of the structure. The main limiting states include:

Loss of bearing capacity due to structural collapse or the occurrence of ultimate deformations ( R );

Loss of integrity as a result of the formation of through cracks or holes in structures through which combustion products or flame penetrate onto an unheated surface ( E );

Loss of heat-insulating ability due to an increase in temperature on an unheated surface of a structure to the maximum values ​​for a given structure ( I );

The fire resistance limit of windows is set only by the time of the onset of the loss of integrity ( E ).

The designation of the fire resistance limit consists of a letter denoting the corresponding limit state ( R , E , I ) and the numbers corresponding to the time of reaching one of these states (the first in time) in minutes.

For instance:

· R 120 - fire resistance limit of 120 min - loss of bearing capacity;

· RE 60 - fire resistance limit of 60 minutes - for loss of bearing capacity and loss of integrity, regardless of which of the two limiting states occurs earlier;

· REI 30 - fire resistance limit of 30 minutes - for the loss of bearing capacity, integrity and thermal insulation capacity, regardless of which of the three limiting states occurs earlier.

If, however, for the construction they are standardized various fire resistance limits various signs of the onset of the limit state, the designation may consist of two or more parts. For instance, R 120 / EI 60 or R 120 / E90 / I 60 .

By fire hazard in accordance with GOST 30403, building structures are divided into four classes:

· K0(non-flammable);

· K1(low fire hazard);

· K2(moderately fire hazardous);

· KZ(fire hazardous).

The fire hazard of structures is established depending on the consequences of exposure to flame on the structure, including such as:

· The presence of a thermal effect from the combustion of construction materials;

· The presence of fiery combustion of gases released during the thermal decomposition of construction materials;

· The size of the damage to the structure;

· Fire hazard of materials from which the structure is made.

The fire resistance of structures affects the fire resistance of a building. Particular attention is paid to the load-bearing elements of the building, which ensure the overall stability and geometric invariability of the building in the event of a fire. These include load-bearing walls, frames, columns, beams, girders, trusses, floors, etc. These structures are subject to the highest fire resistance requirements, but only with regard to their loss of bearing capacity ... According to the limits of fire resistance of building structures, the degree of fire resistance of buildings and structures is assigned. In accordance with SNiP 21-01-97, four degrees are established. I is characterized by the presence of basic building structures with a high fire resistance limit (from R 120, REI 120 to RE 30). The least fire-resistant - IV degree - the limits of fire resistance for it are not even set (for IV they are less than 15 minutes).

An important means of preventing fires and explosions is fire prevention, which is based on an assessment of the explosion and fire hazard of production facilities. This assessment allows you to assign organizational and technical measures. Currently, according to NTB 105-95, production is categorized depending on the premises, buildings and structures in which they are located and on the combustible properties of substances and materials used in production. Explosion-and-fire-hazardous premises are divided into separate categories according to the overpressure of the explosion, because this parameter significantly affects the development of a fire in a building

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