Types of fire detectors. Fire smoke detector: models, characteristics, principle of operation Individual fire detector

Good afternoon, Dear Readers and colleagues! Analyzing the letters and questions that come in a personal and email from our Readers, it became clear to me that our blog is read not only by experts, specialists and designers, but also by people who are quite far from understanding the essence of the constituent units and elements fire fighting systems. However, given the interest of this category of Readers in our blog, which we cannot but approve, today I open a series of articles “Fire Automation”. In these articles, I will try to give information about the constituent elements, nodes and types of fire-fighting automation in the simplest possible way. The first article in the cycle is "fire detectors - type, description". So, let's start in order.

• fire detectors

The main element of the fire alarm system is a device that detects a fire by any of its signs. These are fire detectors, the quality of which fully determines the efficiency of the entire system, the presence of "false alarms" (false alarms of the alarm system), the time of fire detection and many more parameters that we will deal with in detail later.

Fire detectors are classified according to the activation parameter and the physical principle of detection. Fire detection uses three basic detector activation parameters:

1. The concentration of smoke particles in the air;
2. Ambient temperature;
3. Open flame radiation.

The physical principle of detection of these parameters is understood as a specific physical process A used to locate a specific activation setting.

1 thermal fire detectors

Thermal fire detectors respond to changes in ambient temperature. They are installed in the following cases:

When, in a controlled volume, the structure of the materials used is such that during combustion it releases more heat than smoke (for example, if the walls in the room are lined with wood panels).

When the spread of smoke is difficult due to tightness (in the cable duct) or the presence of active ventilation that weathers the primary sign of fire detection - smoke.

When the use of a smoke detector is not possible due to the presence of signs leading to a false alarm or failure of the smoke detector ( low temperature, high humidity, etc.).

When there is a high concentration of any aerosol particles in the air that have nothing to do with combustion processes (for example, soot from working machines in a garage, the presence of steam or flour suspended in the air in flour mills).

The simplest and cheapest are maximum thermal fire detectors– devices that generate an alarm when a predetermined maximum allowable temperature. The simplest devices consist of a soldered contact of two conductors. When heated, the soldering tin melts, the electrical circuit is broken, due to which an alarm is generated. The detectors of this type mainly include devices of domestic production, such as IP-105 and similar ones.Typically, the maximum temperature set in them is 75 o C.In more complex models, a temperature-sensitive semiconductor element is used, which forms a closed electrical circuit with a negative temperature resistance, to which a certain potential difference is applied. As the temperature rises, the resistance of the circuit drops and more current flows through it. The current value is monitored and an alarm is generated if the set value is exceeded. The main advantages of these devices in comparison with the previous ones are more high speed response, as well as the fact that the value of the maximum temperature can take various meanings and when an alarm is generated, there is no destruction of the instrument. Usually a whole line of such devices is offered with different response temperatures - for example, 60, 65, 75, 80, 100 and even 120-180 ° C (used in saunas, for example).

The fastest in terms of response time and stable in operation are differential heat fire detectors. They have two thermoelements, one of which is located inside the detector body and does not have direct contact with environment, and the second is taken out. The currents flowing through these two circuits are fed to the inputs of a differential amplifier, at the output of which a signal is formed that is proportional to the difference in currents at the inputs.

Under normal conditions, the temperature inside and outside is almost the same and the signal at the output of the differential amplifier is small. In the event of a fire, the current flowing through the external circuit increases sharply, while in the internal circuit it remains practically unchanged, which leads to an imbalance in the currents and, accordingly, a sharp increase in the signal at the output of the differential amplifier and the formation of an alarm signal.

The use of an internal thermocouple eliminates the effect of gradual temperature changes caused by natural causes that have nothing to do with the presence of a fire. Thus, the greatest reliability of work is provided.

There are situations when the use of the heat detectors discussed above is either inefficient or impossible at all: cable ducts, large production workshops, tanks in the petrochemical industry, transport depots, chemical reactors, etc. In all these cases, it is necessary to use linear heat detectors. The operation of this type of device is based on the use of a special sensor cable, which consists of four copper conductors with sheaths of special material with a negative temperature coefficient.

The conductors are packed in a common casing so that they are in close contact with their shells. The wires are connected at the end of the line in pairs with each other, forming two loops that are in contact with the shells.

As the temperature increases, the shells reduce their resistance, changing the total resistance between the loops, which is measured by a special results processing unit. According to the magnitude of this resistance, a decision is made about the presence of ignition. The longer the cable, the higher the sensitivity of the device.

Multi-point thermal fire detectors is a circuit of thermocouples that measure ambient temperature each in its specific location, and the coordination and control unit, which is part of the multi-point fire detector, analyzes the amplitude of the temperature difference over the entire length of the thermocouple circuit and generates a “Fire” notification based on the results of the analysis.

2. Smoke detectors

Smoke detectors react to the appearance of a given concentration of smoke particles in the air. Since the concept of "smoke" is less elementary than the basic concept of "temperature", it is worth considering it in more detail. Smoke is a collection of aerosol particles of various nature, released during the combustion process. various materials. It is uniquely described by four parameters: chemical composition particles, their size, concentration and speed of movement. Composition, size and concentration depend on chemical nature burning substance, and the concentration and speed of movement depend on the distribution of air flows in controlled area. The smoke detector itself determines only one parameter out of four: the concentration of smoke particles up to a certain top speed their movements (usually not higher than 10 m/s). However, since the composition of the particles can be very different, there are two types of smoke detectors with different physical detection principles: optical and ionization, which we will dwell on in more detail ..

Ionization smoke detectors contain a source of weak radioactive radiation (americium-241 is most often used) with an ultra-low level of the order of 0.9 μCurie (below background radiation).

The flow of radioactive particles is directed to two separate chambers: a control chamber isolated from the environment and a measurement chamber open to outside air. When smoke particles enter the measuring chamber, the current flowing through it decreases, since this leads to a decrease in the path length of alpha particles and an increase in ion recombination. For processing, the difference signal between the measuring and control chambers is used.

It is important to emphasize that ionization detectors do not cause the slightest harm to human health, and the only difficulty in working with them is the need for special burial after the end of their service life (which is at least 5 years).

Optical smoke detectors use the optical effect of scattering of infrared radiation on smoke particles.

The measuring chamber of this device contains an IR LED and a photodetector, oriented relative to each other so that the radiation of the LED under normal conditions practically does not fall on the photodetector. To exclude the possibility of accidental ingress of extraneous light radiation, the photodetector and the LED are located in a special optical chamber, which is part of the design of the optical smoke detector. When particles of smoke appear in the air, they enter the optical chamber and chaotic scattering of the diode radiation occurs on them, as a result of which part of it begins to fall on the photodetector, providing the formation of an electrical signal. The level of this signal is the higher, the greater the concentration of scattering smoke particles in the air inside the smoke chamber of the detector. When the signal exceeds a certain threshold, the detector makes a decision about the presence of fire.

It is important to note that for the stable operation of an optical detector, the degree of perfection of the design of the optical camera is very important, since it is it that determines the degree of perfection of the entire device and, in many respects, its cost is determined precisely by the complexity of the configuration of this very camera.

For all smoke detectors, the shape of the detector housing is important, since, on the one hand, the design of the housing should ensure maximum inaccessibility to contamination and ease of cleaning from dust. On the other hand, of course, it is necessary to provide good aerodynamic characteristics for efficient smoke suction.

Linear smoke detectors are an active infrared barrier, when smoke particles hit the beam, the signal from the output of the photodetector decreases. This type of smoke detector is used in cases where it is either necessary to cover large linear spaces with a minimum number of detectors, or with sufficiently high ceilings (from 4 to 12 meters), when the time of smoke detection by a detector with a closed smoke chamber is long. Also play the role of interference in the areas, such as large production workshops, which do not allow to fully carry out Maintenance conventional smoke detectors placed over the area of ​​the entire workshop ceiling. In these cases, an emitter is hung on the wall, on the opposite side on the wall - a receiver or reflector, and the beam of the linear smoke detector covers the entire length (up to 100 meters).

3. Combined fire detectors

The protected area may contain materials with different characteristics combustion, which involves the use of different physical principles for detecting the ignition of these materials. That is why it is planned to install fire detectors with a different principle for detecting fire factors. In order to reduce the cost and reduce the bulkiness of the system, special combined fire detectors are used, in which several types of fire detectors are assembled in a single housing.

This smoke sensor model has two advantages: firstly, it can detect a very wide range of different combustible materials, and secondly, this sensor can distinguish between genuine combustion products and interfering particles such as water vapor. This is made possible by the use of bi-angle light scattering technology. Typically, smoke detectors monitor light from a single angle, so they can only reliably identify certain types of smoke. The latest generation of sensors work on two angles of light reflection, which allows you to measure and analyze the ratio of forward and backscatter light characteristics, identifying smoke types and reducing the number of false alarms. The fact is that the intensity of the signals measured by forward and backward scattered light varies depending on the type of combustible material. The ratio of direct scattered light to reversed light is greater for dark smokes (eg, open combustion of diesel fuel) than for light types of smoke (eg, smoldering fires), and even higher for dry substances like flour dust. Sensors that detect light from a single angle cannot calculate this ratio and are thus unable to classify smoke types. In the new type of detectors, interfering particles can be precisely differentiated from genuine combustion products, reducing the number of false alarms to a minimum.

Some manufacturers also produce so-called three-dimensional combined fire detectors, in which smoke optical, smoke ionization and thermal detection principles are combined in one housing.

4. flame fire detectors

Sometimes it is necessary to register the presence of a fire at the first appearance of a flame (before the surrounding materials burn). In this case, flame detectors must be used.

An open flame contains characteristic radiation in both the ultraviolet and infrared parts of the spectrum. Accordingly, there are two types of these devices: ultraviolet and infrared.

UV Flame Detectors using a high-voltage gas-discharge indicator, the radiation power is constantly monitored in the spectral range of 220-280 μm. When a fire occurs, the intensity of the discharges between the indicator electrodes increases sharply, which is fixed when the emitter exceeds the threshold. One such detector can control up to 200 sq. m of surface at an installation height of up to 20 m. The inertia of its operation does not exceed 5 seconds.

Infrared flame detectors using an IR sensitive element and an optical focusing system, characteristic bursts of IR radiation are recorded when an open flame appears. This device allows you to determine within 3 seconds the presence of a flame with a size of 10 cm at a distance of up to 20 m at a viewing angle of 90 °.

5. manual fire detectors

Manual fire detectors are used to force the system into fire detection mode by a person. They are made in the form of levers or buttons, covered with transparent materials (plastic or glass), easily and without harm to health broken or opened in case of fire. Installed near escape routes. Actually, under mechanical action, the circuit shunted by the load resistor opens (or closes) and a “fire” signal is generated.

6. aspiration fire detectors

Aspiration fire detectors can be classified as smoke fire detectors by distinguishing the fire factor. However, according to the principle of operation, aspiration detectors are much more complicated than conventional smoke detectors. In the following articles, we will definitely return in more detail to the design, parameters and areas of use of aspiration detectors. For now, it is enough to mention that aspiration detectors include the air environment analysis unit itself, a fan that drives the air environment through the detector analysis area, and special nozzles with suction nozzles for sampling the environment at the location.

Well, for the closest acquaintance, all the main types of fire detectors used in automatic fire alarm systems. In the continuation of the series of articles "Fire Automation", we will consider other components of fire detection systems.

In the meantime, this is the end of the article “fire detectors - type, description”. I would be glad if in this article you learned some useful information. I allow copying an article for placement on other resources on the Internet only if all the links to our site listed below are preserved, I suggest that you familiarize yourself with other articles of our blog using the links:

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A huge hello to everyone! How are you, dear readers, how are you? Raise it to yourself by looking at funny pictures related to firefighters. Vladimir Raichev is with you today and as always, and today we will consider the main types of fire detectors.

Almost all devices can be divided into two types - automated and manual. Absolutely all detectors during installation work equipped with at least one manual call point. They should be used by the person who first noticed the fire of something in the room.

The second type provides for the automatic activation of a siren or other means of warning. But according to the principle of work, they can be divided into:

• thermal,
• analyzer,
• spectral.

Most often, it is smoke detectors that are installed, although this is not always effective, since at the time of burning some substances practically do not emit smoke.

Assembly of the device and principles of operation of the main detectors

The principle of operation of any sensor, whose main function is to detect the formation of smoke in a room, is to install it in two separate detector chambers. One of them is completely sealed, while the second is connected to the environment, while constantly comparing the air in the system.

An infrared sensor and a receiving device are installed in each of the chambers, which independently generates a current of a certain value. If smoke enters the chamber, infrared radiation is reflected from it, while the magnitude of the current changes. When a significant difference is reached, an alarm is triggered, which enters the control point.

Majority modern models have a self-functioning microprocessor circuit that analyzes all incoming data, as well as the shape and level of the signal. This is done to minimize false alarms.

The main disadvantages of smoke detectors include the inefficiency of data processing if the incoming smoke particles are too large, or the fire is not accompanied by the formation of smoke.

It is not possible to use this system in very dusty environments. Since dust particles are too large, they will cause false alarms if they enter the system. There may be a backlash, and a signal due to the constant movement of large dust particles simply will not work at the time of danger.

No less popular is the heat detector. In this case, the sensors will react to the temperature, which rises to a large extent during the combustion process.

According to the type of action, differential and maximum are distinguished. The first sensor is triggered when the temperature in the room starts to rise at a certain rate. The second reacts when the temperature level in the room is violated. This is done at the software level.

Selecting the type of automatic fire alarm

Before starting installation work, you should decide on the choice of sensors on which the alarm system will depend. An addressable or analogue alarm system can be installed.

The analog system will perfectly fit into the interior of 2-3 rooms. At the same time, it has a very low cost and easily recognizes signs of fire.

An address scheme will be needed when protecting a building or structure located over a large area. At the moment of ignition, an alarm signal is sent to the control panel. In addition, the system, with an accuracy of up to a meter, indicates the very place of ignition, which allows you to eliminate the fire in the shortest possible time.

Of course, addressable alarm systems are the most modern, they have much greater accuracy in determining the location of a fire, since one sensor corresponds to any room or part of it, while analog alarm systems can have several rooms connected to one loop.

I already wrote more about automatic fire alarms and the principle of its operation in this article.

Today I have everything, I hope that now it has become clearer how fire detectors work and what types they are. As a confirmation, I would like to ask, from the point of view of logic, what type of detectors should be installed in a catering kitchen? Answer in the comments.

Subscribe to blog updates so as not to miss anything important and interesting, share the article with your friends in in social networks, see you again on the pages of my security blog, bye-bye.

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. This:

• - 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, industrial and warehouses with the circulation of materials prone to the release of 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. In 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 other external factors. To check the photodetector, special laser pointers or aerosols that allow you to remotely monitor the performance of the detector.

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.

The fire detector is technical system for fire detection and notification. In practice, this term often means only a point device installed in the observed room. However, this is only partly true when a stand-alone device immediately gives a signal. Typically, a system of many sensors, transmission networks and other elements is used, so the sensor itself is only part of the fire alarm system.

Device models

A fire hazard can arise anywhere - in an apartment, a paper archive, a high-tech center (for example, a television studio), or at work, and in each case, the fire spreads in its own way.

To protect property and people's lives, different types of fire detectors have been developed, differing in the principle of operation (controlled sign, technology), accuracy and complexity of equipment, drive (manual or automatic) and other characteristics (explosion-proof, reusable sensors, etc.) .

The most common models are triggered by an increase in temperature or amount of smoke.. The maximum reliability is provided by analogue addressable systems, which transmit not a formal exceedance of a given threshold, but numerical indicators of the environment, providing for the connection of devices for monitoring data.

To choose best option for a particular facility, you need to know what types of fire detectors are commonly used and what their strengths and weaknesses are.

Classification by sensor type

Depending on the need to equip an object with a fire alarm, those types of sensors are selected that are able to register a signal in the shortest possible time. There is the following classification of detectors according to the type of sensor built into them.

• thermal

The signal is given when the threshold temperature of the medium rises. Possible different variants versions:

1. point. Sensor for monitoring fire safety in a small area;
2. multipoint. Connection to one line of many sensors with a given step between them;
3. linear (thermal cable). Solid construction that responds to rising temperatures along its entire length. The sensor can be a gas-filled tube with a pressure sensor, or wires insulated with fusible material that close the lines when the temperature threshold is exceeded.

For these devices, it is recommended to mount under the ceiling where the temperature is highest. There is also some delay between the start of a fire and the arrival of a signal. The point sensor can send an address signal to localize the source of fire.

• smoke

The fire signal is sent to the control panel when the composition of the air, that is, its smoke content, changes. Several options are possible:

1. optical, point. A light emitter and a receiving photocell are built into the detector, located not on the same line. When smoke enters the interior, light is reflected from its particles, and the radiation reaches the photocell, triggering the fire alarm system;
2. optical, linear. The emitter and the receiving element are on the same line, but spaced apart in the room. When smoke crosses the beam, the signal weakens, triggering a fire warning;
3. aspiration. In the controlled room, only the air intake device is installed, and the sensor-analyzer is located in another place;
4. radioisotope. A chamber irradiated with a radioactive substance is built into the sensors, inside which an ionization current is created between two electrodes. When smoke particles enter the air of the chamber, the speed of the ionization current decreases, and a fire alarm is triggered;

Fire detection by smoke allows you to warn about a fire much earlier. The point fire detector will only work with gray smoke, because black smoke absorbs light. The linear sensor monitors a fairly large area and works even with black smoke, but it costs much more.

The aspiration sensor with forced air intake is installed in especially clean rooms (operating rooms, control centers, TV studios, museums, etc.), where other types of detectors cannot be installed, but it is important to detect a fire in the early stages in order to protect expensive equipment. Radioisotope sensors work with both types of smoke, but their life is limited, and in older models, radiation is hazardous to health. Dust on the object can cause false alarms security and fire alarm.

• flame

Responds to electromagnetic radiation smoldering hearth or open flame within a given area. The device works well in open areas and in rooms with high heat exchange, where the use of smoke and heat detectors is not possible.

• gas

The gas fire detector responds to changes in air composition by detecting gases released during the combustion of materials: hydrocarbon compounds, carbon monoxide, etc. These devices are able to detect a fire at an early stage.

• manual

Human activated. Such a device is effective in places with a large crowd of people.

Since the types of fire detectors described above can use different principles of operation, their marking indicates both the controlled fire sign (1st digit of the abbreviation) and the switching method used (2-3 digit). The most common are the following triggering technologies:

General principle of operation	Technologies used
Fusible or combustible links	As the temperature rises, the insulating layer disappears and the contact closes.
Change of substance at different temperatures	Expansion of a liquid/gas with temperature (pressure is measured in a filled tube or other container) or linear expansion solids(option - change in the modulus of elasticity); shape memory effect (when heated, the body bends and closes contact or reflects light in the right direction); change in the optical conductivity of materials depending on temperature.
Change in electrical conductivity characteristics at different temperatures	Effect of temperature on electrical resistance and magnetic induction; thermo-EMF effect (emergence of an electromotive force in a closed circuit of two different conductors when one of them is heated); Hall effect (non-contact measurement magnetic field in semiconductors, which varies with temperature).
Ferroelectrics	Spontaneous occurrence of polarization of some crystals in a certain temperature range.
Resonance-acoustic control	Ultrasonic detectors, the sensors of which are both receivers and emitters of ultrasonic vibrations.
Optic	Tracking changes in the environment in the optical wave range inside the detector (smoke sensor) or in the room itself (flame sensor); infrared and ultraviolet sensors.
radioisotope	Changes in the electromagnetic field when foreign elements (smoke particles) enter.

To improve security and fire safety, different types of fire detectors are simultaneously used. For example, the design of linear sensors covers a large area, but does not allow localizing the source of fire, like point addressable sensors, so the installation of devices of both types is often designed at the same object. Sometimes it is necessary to protect the detector itself, and for special hazardous conditions manufacture explosion-proof parts and housing.

Extra options

Fire alarm detectors also differ in the features of installation and operation of products.

Installation:

• stand-alone detector includes a sensor, batteries and;
• part of the system (the sensor only monitors changes in the environment and transmits a signal to another module);
• external/hidden sensor (the device can be located inside the air duct, under the enclosure of the equipment, on the ceiling, above the moving conveyor belt, and in other places).

The automatic fire detector is technical device, which is installed in the house, in production, in the office, on social facilities and premises for other purposes subject to fire hazard control. The device analyzes one or more parameters that are signs of a fire hazard, such as smoke or a critical increase in temperature. When factors appear, it emits an alarm signal with a sound or transmits it to the control panel. So, the fire detector is the most important component on any object. From him right choice, opportunities and technical parameters depend human lives and safety of property.

Important! The correct choice of automatic signaling for a particular object depends on how timely the equipment will notify people about an emergency.

Today, a wide variety of fire detection and warning devices are presented on the fire safety market. Their classification is multi-structural, we present it in full. So, the types of fire detectors are distinguished:

By signal type:

• 1-mode device transmits a signal when reaching external factor given parameter;
• A 2-mode device can report two events: there is a fire in the room or not;
• multi-mode sirens can report their malfunction or dustiness;
• analog models not only notify about changes in the parameter of the external factor, but also report on its quantitative values;
• hand signaling device - a device that is activated manually.

By design:

• this is a type of device that sends a signal along the wire;
• wireless models transmit a signal via mobile communications or radio;
• point devices with 1 sensor;
• linear devices monitor the state of a zone located along a line, for example, a conveyor.

By the type of change in the external factor:

• threshold models respond when an external parameter reaches a given value;
• differential devices respond to the dynamics of parameter changes;
• combined devices monitor several external factors at once.

By localization:

• a point fire detector monitors the external factor with a single sensor;
• linear devices monitor the condition of the premises along the line;
• multipoint detectors are a system of several sensors.

By the type of parameter monitored by the devices:

• the smoke detector is the most popular device today, since the appearance of smoke in a room is the main sign of a fire, it will help to detect even smoldering electrical wiring, its principle of operation is based on the analysis of air transparency parameters; aspiration models are the most reliable, accurate and in demand;
• thermal fire alarms are automatically triggered when the temperature in the room reaches certain values;
• flame detectors allow to control the appearance of open fire, distinguish between ultraviolet and infrared devices, they are mainly used in rooms with high ceilings, in workshops where fire is used in technological processes, in warehouse terminals, halls where many machines are located, in hangars and similar facilities;
• The gas analyzer is designed to determine the presence of carbon monoxide in the room.

There are other varieties: pyrotechnic detectors, ionization sensors, electrical induction devices and other devices. These modifications are less common.

By way of eating:

• on a loop, when all sensors receive power all together;
• through a dedicated electrical line;
• The devices are battery powered.

On a note! The first devices are manual alarms, they were born back in late XIX century. Devices in the amount of about 700 pieces were installed in the capital of Great Britain. Then thermal sensors were developed. But these devices have not lost their relevance even today, since their operational characteristics are high: fast response, stable performance.

Various buildings and rooms are characterized by different fire load. It depends on the materials used in the construction and repair, the technological processes taking place in them, the characteristics of the stored materials and objects. For example, in a hardware store that sells paints and varnishes, it is better to install flame detectors, since these materials are prone to ignition. In a warehouse where fabrics are stored, it is advisable to use a fire smoke detector.

Features of the installation of fire detectors

All aspects of installation are regulated normative documents, in particular SP5.13130-2009. It prescribes the actions of specialists, starting with the creation of the project. Basic Rules:

• the choice of equipment must be made depending on the purpose of a particular room, the characteristics of the building and the fire load;
• the document limits the choice of annunciators to three types - reacting to a flame, controlling smoke, fixing the temperature, other varieties are installed as needed.

All aspects of the choice of sensors for rooms are regulated by Appendix "M" of the above document. The efficiency and performance of the warning system depends not only on the correct choice of sensors, but also on proper installation in the room. In order to avoid "false positives" or vice versa, the absence of a signal when dangerous factors during installation, the following principles should be followed:

• it is better to place warning equipment on the ceiling, if this is not possible, they can be installed on walls, tension cables or columns, but not further than 0.3 meters from the upper ceiling;
• the distance to the wall from the ceiling fixture must be at least 0.1 meters;
• thermal and smoke devices should be mounted on those places of the ceiling through which air flows, for example, not far from the ventilation grilles;
• the number of annunciators in one room is not limited by the standards, there is only a lower limit - if the area of ​​​​the room is more than 10 m2, at least 2 devices must be installed;
• as part of the electrical circuit that transmits the signal, more than 5 annunciators at production sites should not be combined, administrative buildings, offices and residential buildings, it is permissible to use 10 devices in one loop;
• if interior items are installed in the room, the upper plane of which is located closer than 0.6 meters from the ceiling, it is mandatory to install a separate device in this area;
• if the layout of the room has complex configurations, it is better to use addressable sensors, since analog devices in such conditions will not cope with the tasks;
• it is better to connect addressable annunciators to the control device according to the radial scheme;
• when installing detectors, ease of access for maintenance should be provided;
• if the sensor cables are laid behind finishing structures, e.g. stretch ceiling, in the space between the floors and facing materials additional devices should be installed on a separate wire;
• the maximum area of ​​\u200b\u200bthe room that one device controls is indicated in its passport, but it is better to use the values ​​\u200b\u200bof the table below, they are regulated for the installation of the GOST fire and security alarm system.

An intrinsically safe circuit must be used to power the detectors. At facilities where there are risks of explosions, devices with protective equipment must be installed. This has been taken into account by the manufacturers. They offer models with one or more types of protection.

Fire smoke detector

Since smoke detectors are used everywhere and are relevant for installation in premises of any purpose, it is worth dwelling on them separately. This type of device has a number of advantages:

• compactness;
• ease of installation and maintenance;
• high sensitivity to smoke.

The principle of operation of a standard smoke fire detector is based on the effect of light scattering by microparticles of smoke. If some of the photons leaving the source begin to be reflected, then fewer of them arrive at the receiver, the microprocessor captures the changes, generates and sends an alarm signal. Linear and point models have sensitive pairs located differently. The most popular smoke detectors in Russia are SDN, APOLLO and APO. Usually, design features are determined in model numbers, for example, the following information is indicated in the IP 212 markings:

• IP - fire detector;
• 2 - analyzes the presence of smoke in the air;
• 12 - optical device.

Model 212-141 detects the presence of smoke in enclosed spaces, even in minimal concentrations. It is switched via a 2-wire loop and works with the control panel control panel. For stable operation, you need a voltage in the range from 9 to 30 V. Another popular device is 212-142, it is characterized by a high response speed, the ability to work in the dark and resistance to temperature changes. Optoelectronic models S-3000 SDN and D700-06-101 are in demand due to their high sensitivity, compactness, absence of false positives and long service life.

When are fire alarms used?

The fires that have become more frequent in recent decades in buildings for various purposes indicate that it is necessary to install at all facilities. These devices are especially needed for places of concentration a large number people, and these are trading and entertainment centers, production and apartment buildings, clinics, schools, etc. The Ministry of Emergency Situations recommends the use of sensors in private homes, this will allow firefighters to come to your aid in a timely manner.