Smoke detector: types, characteristics, installation. Use of indoor smoke detectors Analogue and addressable systems

Today's Russian market presents to the attention of consumers the widest choice of products in the field of production fire alarm, allowing you to recognize the fire accurately, efficiently and in the first seconds of its occurrence. There are several types of smoke detectors, which have their own advantages and disadvantages, depending on the principle of their operation.

Device characteristics

A smoke detector is an alarm system required to detect and report a fire. necessary in all administrative buildings and social facilities, for timely warning of a fire that has begun and its quick elimination. The article below discusses the main types of detectors, in particular, smoke detectors.

AT fire fighting system There are several types of detectors:

• smoke (smoke recognition) - are divided into optical and ionization;
• thermal (responding to a rapid increase in temperature): maximum, differential and maximum differential.
• flame (open flame detection). Includes 4 classes of flame detection range. Class 1 includes devices that react to fire from 25 meters or more. By the 4th class - from 8 meters.
• (triggered in the presence of gas);
• combined (including all types at once);

How separate view, there are manual call points, which are a button or fire alarm lever, which is activated using manual control.

Fire smoke detectors are triggered when the smallest particles of smoke hit the optical-electronic camera of the sensor. The reaction rate of the device depends on their saturation. The principle of operation of smoke devices is based on the fact that the beam being sent is scattered in the presence of smoke particles in the air. The device detects this change in radiation with a special sensor. The slightest "fogging" leads to the activation of the alarm system.

How a smoke detector works

These devices are used in households, in crowded places (schools, hospitals, shopping centers) in production.

The fire smoke detector is very popular due to its high sensitivity, as well as rapid response to the source of fire. Its mechanism practically does not fail, and the number of false alarms is reduced to a minimum.

Types of smoke alarm devices

From the method of detecting a fire, smoke detectors are divided into: optical and ionization.

Optical

Optical detectors function by monitoring the physical composition of the air mass and trapping combustion products in it. These sensors include:

• Point

Determine the source of ignition in a small specific area. Sensors of this type capture smoke by examining the reflected infrared rays in a special optical chamber. The smoke chamber consists of an infrared radiation device and a receiver for examining the reflected air. Point smoke detectors are diverse in shapes and models.

Autonomous point smoke fire detectors and radio channel are distinguished.

Equipped with rechargeable batteries and sound sensors. Work independently, without supervision of the operator. They are easy to use and low cost. The principle of their work is the ingress of smoke particles on the optical camera. The device is housed in a plastic case with various designs matching the interior of the room. Works both autonomously and from the network.

Radio channel point detectors operate on a specific radio wave, through which, in the event of a fire, a signal is transmitted to the operator's console. Work from batteries. The distance between the sensors is 4-5 meters.

• Linear

Monitor the room for fire in the linear zone. Used in industrial and large facilities (shopping centers, offices, public institutions). They are characterized by high sensitivity in detecting smoke. Linear smoke detectors are divided into two-component and one-component.

Two-component sensors consist of a receiver and a transmitter located in different sides premises. As soon as smoke enters the controlled area, the fire alarm mechanism is activated.

One-component devices are a single unit with a passive reflector that analyzes the state of the air.

Detect all types of smoke and are efficient in operation.

• Aspiration

The most complex and expensive type of device of all types of smoke detectors. They are a powerful case, inside of which there is a point laser detector, and air sampling tubes. They forcibly produce and analyze the air from the room in a fast mode. are used on important objects (archives, museums, ships) and, accordingly, are very high in price.

Ionization

The ionization fire smoke detector consists of two air intake chambers and produces radiation that is safe for human life and health. Fresh air passes through both chambers. If smoke appears in the room, then its particles will linger in the 1st chamber, causing a decrease in the current strength in the 2nd. This is how the fire alarm goes off. There are 2 types of such alarms: radioisotope and electric induction.

Most often, ionization sensors are used on large warehouses and in the manufacturing sector.

Radioisotope smoke detectors report a fire after the appearance and effect of smoke on the current. These sensors ionize the air space with a special radioactive substance. When smoke enters one of the chambers of the device, it dissolves in charged current particles, as a result of which, the force of the voltage inside the chamber decreases and a signal is triggered.

Detectors ps automatic smoke photoelectric radioisotope better than all other types of devices detect "black" smoke.

Electric induction devices pass air from the controlled room into the charging chamber through the gas duct and analyze its composition. The particles of the intake air are affected by a unipolar charge, and they acquire a space charge.

Electric induction sensors investigate the duration and amplitude of the movement of air microparticles. If there is a deviation from the set parameters, the contact mechanism instantly closes and a fire signal is transmitted to control point where the operator monitors the operation of the system.

Electric induction detectors are used at critical facilities, including the ISS.

Device

Fire notification can be targeted or non-targeted. It depends on how the specific detector is connected to the fire system.

They transmit a signal to the control panel, where the place of the fire is determined, since all devices are identified in the system under a certain number. Used in large buildings and industrial premises.

Conventional smoke detectors emit only an audible signal, and you can determine the location of the fire only by focusing on it.

The fire alarm consists of plastic case, where the optical camera, light receiver and refractive shutters are located. Air particles entering the camera reflect radiation from the light source. The sensor circuit analyzes the composition and density of the glow by means of a light receiver. When smoke is detected, an alarm is triggered. Refractive shutters protect the device from excess light and from dust in the air.

A large accumulation of dust particles reduces the sensitivity of the detector and can lead to frequent failures. Therefore, it is important to regularly wipe the device from dust.

Optical smoke detectors can be equipped with LED and laser light emitters.

Ionization detectors represent a chamber with two plates under current. The current comes from an ionization source: a coil or a radioactive isotope. If smoke enters the chamber, the voltage between the plates decreases and the fire alarm sensor is activated.

Where and what types should be used?

AT residential buildings, as a rule, optical point devices are installed.

In a large volume space, optical linear sensors with an address type of notification are used.

At especially important objects, optical aspiration fire alarm detectors are more often placed, capable of detecting a fire that has begun in a matter of seconds.

Installation

When buying and installing smoke fire detectors, you need to pay attention to their main characteristics:

• warranty service life;
• material;
• type of device;
• inertia and response speed;
• sensitivity;
• power consumption;
• working distance;
• coverage area.

The installation and number of fire detectors depends on the area of ​​the room, the height of the ceilings, the area of ​​the controlled zone of the sensor, and the presence of dangerous zones.

At least 2 fire detectors are installed in one room. One device is used when: a) the area of ​​the room is small and corresponds to the covered area of ​​the sensor; b) if an addressable fire alarm system is installed.

On average, any sensor covers an area of ​​55 sq.m. (with a ceiling height of 10-12 m) up to 85 sq.m. (ceiling height 3-3.5 m). If the ceilings are more than 12 meters, fire detectors are mounted in two levels - on the walls / on the ceiling. If point devices are installed at the top, then on the walls they are mainly linear.

Fire detectors are located under ceilings and at a maximum distance from walls of 450 cm. The distance between two smoke detectors must not exceed 900 cm.

If the ceilings are suspended, then smoke detectors are mounted between two ceilings and at least 1 meter from the vent. If the room is irregularly shaped or has non-standard engineering structures, the number of fire detectors should be increased.

Ionization fire detector - it's high tech automatic device to register a fire source by the appearance in the gas-air environment of the protected room of volatile products of the combustion process - the smallest particles of soot, burning. This detection method is based on the property of ionized air to attract smoke particles, which gave rise to such a name.

In terms of its effectiveness, this is one of the last stages of technical development, comparable in sensitivity, speed / inertia of detecting the characteristic signs of a combustion process with the formation of fumes, only with gas, aspiration, flow sensors; exceeding the indicators of optical-electronic devices intended for the same purposes.

Ionization fire detectors are able to detect a fire not only at the earliest stage by the appearance of volatile particles of the combustion reaction, but also react to any size; as well as the color depending on the physical and chemical parameters of the fire load in the protected premises, the so-called gray and black smoke; which is not available to most other automatic devices that detect the formation of a smoke stream.

Due to the complexity of production, technical control when creating such devices; the need for disposal / decontamination of expired ionization fire detectors only at specialized enterprises of the nuclear industry, prerequisites have been created for high cost products.

Due to the presence in them, albeit within the permissible state norms, of a small amount of radioactive substances inside miniature radioisotope emitters, which are an integral element of the design in most product models; partly due to the formed prejudiced public opinion in our country, they are not mass-produced.

However, their production continues abroad, and duly certified products can be purchased at Russian market fire-technical products.

Smoke-ionization fire detector

According to the definition given in, this is an automatic fire detection device, the method of operation of which is based on a change in the values ​​​​of the electric current passing through artificially ionized air, when smoke particles appear in them, formed during the combustion of solid, liquid materials.

According to the controlled sign of fire, product design, technical device of sensitive elements of sensors, method of detecting smoke particles, ionization fire detectors include two types:

• Radioisotope.

This is a smoke fire detector that is triggered due to the impact of combustion products on the ionization current of the detector's internal working chamber. The principle of operation of a radioisotope detector is based on the ionization of the chamber air when it is irradiated with a radioactive substance. The principle of operation of a radioisotope detector is based on the ionization of the chamber air when it is irradiated with a radioactive substance. When oppositely charged electrodes are introduced into such a chamber, an ionization current arises. Charged particles "stick" to heavier particles of smoke, reducing their mobility - the ionization current decreases. Its decrease to a certain value is perceived by the detector as an "alarm" signal.

Such a detector is effective in fumes of any nature. However, along with the advantages described above, radioisotope detectors have significant disadvantage which should not be forgotten. We are talking about the use of a source of radioactive radiation in the design of detectors. In this regard, there are problems of compliance with safety measures during operation, storage and transportation, as well as disposal of detectors after the end of their service life. Effective for detecting fires accompanied by the appearance of the so-called "black" types of smoke, characterized by high level light absorption.

• Electroinduction.

Aerosol particles are sucked in from environment into a cylindrical tube (gas duct) using a small-sized electric pump and enter the charging chamber. Under the influence of a unipolar corona discharge, the particles acquire a volumetric electric charge and, moving further along the gas duct, enter the measuring chamber, where an electrical signal is induced on its measuring electrode, which is proportional to the volumetric charge of the particles and, consequently, their concentration. The signal from the measuring chamber enters the preamplifier and then to the signal processing and comparison unit. The sensor selects the signal by speed, amplitude and duration and provides information when the specified thresholds are exceeded in the form of a contact relay closing.

1. high voltage modulator.
2. Voltage regulator.
3. Power Supply.
4. Amplifier.
5. Block of information processing.
6. Charging chamber, electrode ring.
7. Charging chamber, electrode needle.
8. Capacitor.
9. Resistor.
10. Resistor.
11. Zener diode.
12. induction electrode.
13. Light-emitting diode.
14. Aerosol consumption booster.
15. F - Output signal.

Structurally, the measuring line is a cylindrical gas duct, at the inlet of which there is a charging chamber of the needle-cylinder type, and at the outlet there is a measuring electrode-ring and an air mixture flow stimulator.

The main parameter of an electrically inductive fire detector, which allows the use of a floating threshold, is its sensitivity, which makes it possible to provide a stable level of an electrical signal proportional to the aerosol weight concentration over its entire possible range of change.

In, on the requirements for the design of APS, AUPT systems, the choice of point smoke fire detectors is recommended to be carried out in accordance with their sensitivity to different types smoke. According to this characteristic indicator, ionization fire detectors are out of competition among similar devices, incl. effectively detect "black" smoke.

The principle of operation of ionization fire detectors

The history of the invention of the smoke radioisotope detector is amazing. In the late 1930s physicist Walter Jaeger was developing an ionization sensor for detecting poison gas. He believed that the ions of air molecules formed under the action of a radioactive element (scheme A, B) would be bound by gas molecules and due to this, the electric current in the device circuit would decrease. However, small concentrations of poisonous gas had no effect on the conductivity in the measuring ionization chamber of the sensor. Walter lit a cigarette in frustration and soon noticed with surprise that a microammeter connected to the sensor recorded a drop in current. It turned out that cigarette smoke particles reproduced the effect that poison gas could not provide (scheme B). This experiment by Walter Jaeger paved the way for the first smoke detector.

It is based on fixing, recording changes in the indicators of the electric current passing through the ionized molecules of the air in the sensitive element of the sensor, when exposed to small particles of volatile products of the combustion reaction.

When such particles enter the sensor chamber of an ionization smoke detector, they are attached to the ions due to the difference in electrical potentials, which reduces their speed and, as a result, the current strength; with a decrease in their number, removal from the sensitive element of the device, the current strength begins to grow.

The decrease in the strength of the electric current passing through the ionized air to the threshold/critical value set by the product settings is perceived by the device as a sign of the detection of a fire source in the controlled area, the protected room; with the formation, transmission of an alarm message to the receiving and control equipment of the APS installation or the control unit of the automatic fire extinguishing system.

How radioisotopes work smoke detectors is based on the ionization of the air in the control chamber of the sensitive element located inside the body of the product, with intense radiation from its low-power narrowly directed source of radioactive radiation; in electric induction fire detectors, air ionization is carried out by a unipolar corona discharge of electric current.

The design of the ionization detector

The most widely used in comparison with the electric induction device, the ionization radioisotope smoke detector consists of the following elements:

• Enclosures made of high quality plastics, such as flame retardant polycarbonate, with air inlets and outlets, flue gases, protected as shallow metal mesh from the penetration of insects, and the shape of the body around them, their location on it to protect against direct air currents.
• Mounting base with electronic printed circuit board, on which two ionization chambers are installed, connected in series in the electrical circuit - control and measurement; control unit with a microcontroller for data processing, signal transmission, device addressing; input/output sliding clamp contacts/terminals for connection to the loop of the APS installation.
• Structurally, the control chamber is located inside the measuring chamber, being a closed volume, protected from the penetration of smoke particles; while the measuring chamber is open, it is designed for free penetration, filtration of the gas-air medium to record the changes taking place in it.

• A compact source of radioactive radiation, often containing a negligible amount of the americium-241 isotope, deposited on a metal foil, installed inside the control chamber. Its radiation penetrates through both chambers, forming positively and negatively charged particles in the air - air ions; in this case, the radioisotope radiation source carries a positive charge, and the external measuring chamber carries a negative charge. When power is supplied to the input contacts of an ionization fire detector, an electric field arises inside it.
• When accumulation on the signal electrode, installed at the border of the connection of the control and measuring smoke chambers, a positive charge of sufficient strength, set by the settings of the microcontroller; it is formed through an analog-to-digital converter, which is part of an electronic integrated circuit, into an alarm signal transmitted to the device / unit of the APS installation.

The current strength in the ionized space inside such a fire detector remains stable only while maintaining normal conditions in the control zone.

At the slightest change in the air, ionization fire detectors react sensitively, activating the entire complex of automatic fire protection, which makes it possible, if not immediately, to eliminate the source of ignition; then give an opportunity to localize it, give time before the arrival of fire departments, minimize material damage.

are mandatory engineering system any building. Not only the safety of property depends on their faultless work, but also, most importantly, the health and life of people. Timely and reliable fire detection gives people the opportunity to evacuate to a safe area, and fire brigades - to quickly start extinguishing the fire, preventing its spread.

Types of detectors

Fire detectors in the composition are designed to detect fire. Depending on the principle of action, they are divided into types. It:

• - reacts to the appearance of smoke in the room;
• thermal sensor - triggered when the set temperature is exceeded;
• flame detector - captures the visible or infrared radiation of the flame;
• gas analyzer - registers such as carbon monoxide.

The correct choice of the detector allows you to timely detect the source of the fire.

Fire load and detector type

Premises for various purposes have their own specifics in the development of a fire and the manifestation of its factors. Of decisive importance is the fire load - all objects and materials in the room. For example, the fire of paints or fuel is accompanied by a bright flame, which can be detected by a flame detector. But the same will not be effective in rooms with the storage of materials prone to smoldering; a smoke detector will react to smoke from smoldering materials.

Smoke detectors

The most common and effective tool fire detection is an automatic smoke detector. After all, the release of smoke is characteristic of the combustion process of many substances, such as paper, wood, textiles, cable products, electronic equipment, etc. These sensors are designed to detect fires accompanied by the release of smoke in the early stages of a fire. Detectors of this type are effective when installed in residential buildings, public buildings, production and storage facilities with the circulation of materials prone to smoke during combustion.

How smoke detectors work

The operation of smoke sensors is based on the scattering of light on microparticles of smoke. The emitter of a sensor, usually an LED, operating in the light or infrared range. It irradiates the air in the smoke chamber, when smoked, part of the light flux is reflected from the smoke particles and scattered. This scattered radiation is recorded on a photodetector. A microprocessor based on a photodetector puts the detector into an alarm state. Depending on the concentration of the emitter and receiver, the detectors can be point and linear. The names of devices of this type begin with "IP 212", followed by the digital designation of the model. In the designation, the letters stand for “fire detector”, the first number 2 is “smoke”, the number 12 is “optical”. Thus, the entire marking "IP 212" means: "Optical smoke detector".

Point smoke detectors

In devices of this type, the emitter and receiver are installed in the same housing on opposite sides of the smoke chamber. The perforation of the sensor body ensures unhindered penetration of smoke into the smoke chamber. Thus, the optical-electronic smoke detector controls the degree of smoke in the room only at one point. This type of sensor is compact, easy to install and efficient. Their main drawback is the limited controlled area, not exceeding 80 sq.m. In most cases, point detectors are installed on the ceiling, in increments depending on the height of the room. But it is possible to install them on the walls, under the ceiling.

Linear smoke detectors

In these sensors, the emitter and receiver are made as separate devices installed on different sides of the room. Thus, the emitter beam passes through the entire room and controls its smoke. As a rule, the range of this type of detectors does not exceed 150 m. There are variants of devices in which the emitter and receiver are installed in the same housing, and their optical axes are directed in the same direction. For the operation of such a detector, an additional reflector (reflector) is used, which is installed on the opposite wall and returns the transmitter beam to the receiver. The linear smoke detector is mainly used to protect long and high spaces, such as halls, indoor arenas, galleries. They are installed on the walls under the ceiling, the emitter on one wall, the receiver on the opposite. AT high rooms, such as atriums, sensors are installed in several tiers.

Sensor sensitivity

The most important parameter of smoke detectors is their sensitivity. It characterizes the ability of the sensor to capture the minimum concentration of smoke particles in the analyzed air. This value is measured in dB and is in the range of 0.05-0.2 dB. The difference between high-quality sensors is the ability to maintain their sensitivity when changing orientation, supply voltage, illumination, temperature, and others. external factors. To check the photodetector, special laser pointers or aerosols are used, which allow remote control of the detector's performance.

Analog and address systems

The detectors are connected by a loop to the control panel, which analyzes their condition and, if triggered, issues an alarm signal. Depending on the method of transmitting their state, the detectors are either analog or addressable.

The analog fire smoke detector is connected in parallel to the loop and, when triggered, sharply reduces its resistance, in other words, short-circuits the loop. This is a loop and is fixed by a control panel. As a rule, the connection of analog detectors is carried out by a two-wire loop, through which power is also supplied. But there are options for connecting in a four-wire scheme. The disadvantage of such a system is the inability to continuously monitor the performance of the detector, in addition, sometimes a loop is triggered without indicating the triggered sensor.

The optoelectronic addressable smoke detector is equipped with a microprocessor that monitors the state of the sensor and, if necessary, corrects its settings. Such sensors are connected to a digital loop, in which each detector is assigned its own number. In such a system, the control panel receives not only data on the detector's operation and its number, but also service information on performance, dust content, etc.

The housings of most modern detectors have built-in LEDs that determine their status by blinking.

Autonomous fire detectors

Often there is no need for installation automatic installation fire alarm, it is enough just to notify people in the same room about the occurrence of a fire. For these purposes, an autonomous smoke detector is intended. These devices combine a smoke sensor and (siren). When the room is filled with smoke, the detector detects the presence of smoke and sound signal alerts people to the presence of a dangerous concentration of smoke. Such sensors are self-powered - built-in batteries, the capacity of which is sufficient to operate for three years.

These detectors are ideal for installation in an apartment or small house. Some models allow you to combine sensors into a small network, for example, within an apartment. On the body of such a sensor there is an LED indicator, the color and frequency of flashing of which indicate its condition.

general characteristics