Design suspended ceiling allows you to hide exhaust ducts, wiring, electrical cables and other communications in the interceiling space, however, this increases the risk of fire. In this connection, the ceiling must be equipped with an automatic fire alarm system.

When is it necessary to install sensors?

Safety standards are constantly changing, so homeowners with suspended ceilings need to regularly monitor new regulations. Thus, some owners are confident that it is the ceiling height that is the fundamental factor in the need to install an alarm. However, this belief is incorrect - the requirements for fire protection do not depend on the height of the ceiling space, but solely on the presence and amount of flammable cable load. Legally, this is regulated by the following regulations:

• set of rules 13130 ​​of 2009 with mandatory Appendix “A”;
• table “A2”, paragraph 11 and note to paragraph 11 (standard “Fire protection”).

How to determine the need for installation:

Step 1. Look behind the ceiling, find the cable providing power, outlet wires or the power network.

Step 2. Choose the largest possible area, more than a meter in one direction. Count the number of cables, taking into account their brands, write down the data.

Step 3. For each type of wire, determine the combustible mass indicators according to any manufacturer's directory cable products, for example, the Kolchuginsky plant.

Step 4. Carry out calculations using the formula: A×B=C, where A is the number of wiring of a certain model and brand, B is the flammable mass, and C is the desired flammability parameter. The calculation is performed separately for each cable type, then all results are summed up.

Step 5. Compare the resulting indicator with legal standards:

• up to 1.5 liters per meter – no need to install sensors on the ceiling;
• from 1.5 to 1.7 l – fire safety is ensured in the form of an independent ceiling alarm loop;
• 1.7 liters and more - it is necessary to install an automatic fire extinguishing system. For ceiling heights less than 0.4 meters, a cable is installed.

In this case, the distance between the base ceiling and the suspended ceiling should be sufficient to accommodate the sensors. It is also important to identify the area with the most dense arrangement of wires and other communications - the cables should be at a distance of at least 30 cm from each other.

In what cases is a fire alarm not required?

The need to install an alarm is always determined solely by the combustible load indicator. However, in regulatory documentation Safety standards also establish a number of other factors under which installation of a fire alarm on a suspended or suspended ceiling is not required:

1. If there are wires hidden in insulated corrugated tubes or special steel boxes.
2. In the case of installation based on a single-core cable and an NG type electrical supply (non-flammable).
3. If there is a single strand of wiring in the suspended ceiling.

Types of fire detectors

Existing sensors have a fairly extensive classification system in accordance with the nuances of the structure of the device and the methods of its functioning. Each of the detectors has its own installation and operation features. So, depending on the type of signal transmitted, sensors are divided into the following categories:

1. Single-mode detectors. Signal danger upon exposure external factor, for example, temperature. Currently they are not used in everyday life.
2. Dual-mode with “Fire” and “No fire” alarms. At the same time, the absence of a fire signal confirms that the device is in working order and is operating normally.
3. Multi-mode with built-in notification programs about device failures.

In addition, detectors are conventionally divided into types according to their location:

1. Spot Appliances They have a single sensor, often built into the housing.
2. Multipoint devices are equipped with multiple detectors.
3. Linear sirens analyze the space along an arbitrary trajectory. They can be single or paired, autonomous or targeted.

Regardless of the classification, all fire detectors are divided into wired and wireless and differ in the type of detector itself - it is this division that is fundamental when choosing a warning system.

Heat detectors

Heat sensors were the first fire prevention devices. They appeared in everyday life back in early XIX century, and at that time looked like two spring-loaded cables with a wax insert in the middle. As the temperature increased, the wax began to melt and the wires shorted, causing an audible alarm. New generation thermal sensors also have melting elements and often use an electrical effect based on the thermocouple principle.

Despite all the advantages of the device, including its low cost, such detectors have one serious drawback - they sound an alarm after the air temperature has risen and a fire has started. It is for this reason that with the development of technology, this type of device gradually lost its relevance.

Smoke detectors

Systems equipped with smoke detectors are by far the most popular fire-fighting devices for use in residential and work areas. Smoke is the first and main sign of a possible fire, which may appear before it occurs. open flame. For example, a faulty electrical wiring is often accompanied by a long process of smoldering with a characteristic caustic fumes. Therefore, this type of sensor helps to identify the source of fire at its first initial stage.

The smoke sensor operates on the principle of detecting changes in the transparency of smoky air. In this case, the device is classified depending on the methods of its operation into linear detectors (working with a directed beam in the optical or ultraviolet range) or point detectors (based on infrared radiation). Point detectors are usually simpler than linear detectors, but less reliable - thick, dark smoke does not reflect infrared rays, so during such a fire the sensor may not respond.

Flame detectors

This type of siren is usually used to provide countermeasures fire safety at production sites. In such rooms, the use of smoke or heat sensors will be difficult due to the constant dustiness of the air or its elevated temperature.

Types of detectors:

1. Infrared. Captures the radiant heat of an open flame. If there are regularly operating sources of air heating, groundless alarm activation is excluded.
2. Ultraviolet. They are used if there are sources of infrared radiation in the room, for example, an electric heater.
3. Sensors that react to the electromagnetic component of the energy released from an open fire.
4. Security ultrasonic devices. Interact with fluctuations in air masses. The operating principle is based on the fact that hot air actively rises upward.

Rules for installation and placement of fire sensors on the ceiling

Accommodation security and fire alarm system(OPS or APS) is regulated by the normative act SP 5.13130.2009 as amended on 06/01/2011. In accordance with this document, installation of devices is carried out exclusively on load-bearing elements(stiffeners) or cables. It is important to take into account that it is strictly prohibited to attach sounders to suspended ceiling slabs - this design has poor mechanical stability and low fire resistance.

Sometimes ceiling sensors are also used to ensure indoor security. This is possible in cases where false ceilings have large perforations. According to safety rules, installation fire detectors behind a suspended ceiling is possible in the following cases:

• in the presence of perforation with an area of ​​40% of the entire surface with a periodically repeating large pattern;
• with a diameter of one perforation hole of at least 1 cm;
• in case the element size suspended structure does not exceed the minimum size of one cell (for example, Armstrong-type ceilings).

If these requirements are not met, fire detectors must be installed on the walls of the room or directly on the surface of the suspended ceiling. In addition, it is necessary to take into account the sensitivity radius of the devices.

1. Installation is carried out according to the “triangular grid” arrangement principle - this will save space and protect the entire surface.
2. When calculating the range of the device, the orientation of the sensitivity zone in the horizontal plane is used. For smoke sensors - 7.5 m, for heat sensors - 5.3 m.
3. The detector, mounted on the base of a suspended structure, must be positioned so that the sensitive element is below the ceiling level. For smoke - 2.5-60 cm, thermal - 2.5-15 cm.
4. The distance from the walls must be at least 0.5 m.

Calculation of the required number of detectors

Before installing smoke sensors, it is necessary to correctly calculate their exact number for a specific room. In this case, it is necessary to take into account the type of devices and the intended connection diagram. It is important to understand that each state's laws will have different installation standards.

In the Russian Federation, it is mandatory to install at least 2 sensors per room. The regulations state that it is recommended to install detectors on each section of the ceiling with a width of 0.75 m or more, as well as on elements of building structures with a protrusion of 0.4 m.

Thus, a separate zone of the inter-ceiling space should be equipped with:

• three sensors, if they are connected to a two-threshold response loop or to three separate loops with a single response threshold;
• four detectors when connected in pairs to two different device loops with the same threshold;
• two devices with an alternating operation circuit.

Despite the fact that point sensors are capable of monitoring up to 25 meters of a room, it is imperative to install at least two of them if they are addressable and at least three if they are analog. This is explained by the fact that the spread of smoke and fire in the ceiling area has its own characteristics, which means that this area is more difficult to control.

Installation procedure

When installing a device, the first thing to determine is required amount sensors and mounting locations, only then does the installation process begin.

In the suspended ceiling

Sensors are most often installed in suspended plasterboard ceilings using the insertion method - the most aesthetically pleasing and convenient way. It is recommended to use heat-resistant cables with NG type braid, copper conductors and minimum cross-section in 0.5 mm. Please note that installing sensors in blind corners between the wall and ceiling is strictly prohibited.

Fire sensor installation diagram:

Step 1. Determining the number of detectors, their approximate location and distance from each other. It should be noted that smoke sensors must be installed both in the suspended structure itself and on it.

Step 2. Fixing sounders is only permissible on a frame or concrete floor in an overhead way. It is possible to insert into a suspended ceiling and fasten it using special mounting rings, but in this case the sensor is additionally fixed with a cable to the ceiling.

Step 3. The device is connected only in the absence of power and in accordance with the diagram indicated on the sensor packaging. Finally, you should check the accuracy of the connection and the performance of the entire system several more times.

In a suspended ceiling

Regulatory documents do not indicate the mandatory location of fire sensors in suspended ceilings; however, the minimum distance from the walls must be maintained. When installing the device, preference should be given to those areas where there will be the greatest coverage of room control, taking into account the range of the sensor.

Installation instructions:

Step 1. Prepare the embedded structure for the suspended ceiling. To do this, flexible metal hangers are screwed to a flat plate of plastic or plywood, with the help of which the platform is attached to the concrete floor.

Step 2. Align the mortgage to the level with the future ceiling. Bring the wiring down.

Step 3. Stretch the fabric. At the location of the platform, glue a thermal ring so that the PVC film does not tear, then cut a hole to install the sensor.

Step 4. Connect the device and check its functionality. Screw the sensor to the platform.

Safety precautions and possible installation problems

Even though the system fire alarm must be installed by a qualified organization in compliance with all requirements and standards; sometimes apartment owners try to install the device themselves. Self-installation fire detectors is possible, but must be observed certain rules security:

1. During installation work It is allowed to use only special stepladders or ladders - any improvised means are strictly prohibited.
2. For installation and maintenance fire safety systems are allowed by specialists with knowledge of the instructions and specifics of the work.
3. Tools used in the process must have insulated handles.
4. First, you need to measure the voltage between phases using a portable voltmeter.
5. Before installing the system elements, be sure to check the strength of the fire detectors on the suspended ceiling or tension structure.

Common problems during installation and operation

Problem #1: malfunction of one detector while all others are working properly.

Remedy: check the installed smoke sensors and, if necessary, remove them. It should be taken into account that if the voltage indicators are different, then the wiring for fire extinguishing and alarm systems should be located in separate boxes. When laid open, the distance between cables and other communication systems should not be less than 0.5 m.

Problem #2: No alarm.

Remedy: check mounting surface, turn the optical indicator of the device towards the main entrance.

Problem #3: Battery failure.

Remedy: if the sensor is installed on the ceiling itself, then changing the power system will be quite easy - you just need to carefully unscrew the device from its platform. When installing the device inside a suspended ceiling, you will need to partially dismantle the ceiling panel.

Thus, the main requirement for installing a fire detector remains its effective subsequent operation. When choosing a device, it is advisable to give preference to reliable manufacturers whose models are guaranteed to last for several years.

It is better for the owner of the premises to rely on qualified specialists who can calculate the number of detectors and create the correct scheme their location - only when proper installation It is possible to operate fire detectors without failures or malfunctions.

Fire detectors are installed only in accordance with developed standards and regulations, compliance with which must be strictly observed. The number and order of arrangement of sensors is prescribed in the set of installation rules dated 2009 (SP 5.13130.2009). The response time of the detectors, as well as the timely evacuation of people, depends on how competently the installation of all fire alarm sensors is carried out.

Regardless of the type of alarm sensor (smoke, heat, flame, etc.), it is recommended to place at least two devices in the same room for more reliable data and to eliminate the possibility of false alarms.

Rules for placing smoke devices

Point type optical smoke detectors are used in medium or small rooms residential buildings, hospitals, hotels, etc.

Linear smoke detectors are used to control large premises: halls, warehouses, halls, airport terminals.

When installing sensors, the characteristics of gas mixtures and the presence of air flows from ventilation shafts or heating devices are taken into account. Some gases (chlorine, butane) concentrate near the floor, but under the influence warm air may accumulate under the ceiling.

The exact location of the detector (near the floor, near the ceiling) is determined by its settings for capturing a specific gas and is indicated in the product passport.

Placement of autonomous detectors

These sensors are used in everyday life to protect living rooms in private houses, apartments, hotel rooms, etc.

One autonomous fire detector covers about 30 sq.m. controlled area, so one device, as a rule, is enough for one room.

Autonomous devices are mounted in an open ceiling space with good air circulation. Installation above doors and in remote corners of the room is not recommended. It is also not advisable for the autonomous detector to be exposed to direct sunlight.

If it is not possible to install the device on the ceiling, then it can be placed on the walls, and the distance to the ceiling should be within 10 - 30 cm.

If there are protrusions in the ceiling space of more than 8 cm, then the controlled area of ​​the device is reduced by 25%.

Installation of light, sound and voice alarms

The fire safety of the building is ensured not only by detectors, but also by information light displays and sound alarms, facilitating the rapid and organized evacuation of people.

The installation of such alarms is also regulated by regulatory documents. Requirements for the installation site of the light board:

Sound alarms can be located both inside and outside the building. They are mounted under the ceiling - 15 cm to the ceiling, at a distance of 2-2.3 meters from the floor.

The reliability and performance of the fire extinguishing system largely depends on the correct installation, compliance with the rules and requirements for the systems. One of mandatory conditions– these are the standards for installing fire detectors, which depend on the type of devices and the characteristics of the protected area.

Calculating the distance between individual detectors and determining the location of their installation is a labor-intensive and important issue that designers have to solve from scratch at each site.

Codes and regulations governing the installation of fire detectors

For guidance and control of the installation issue fire fighting equipment use various regulations, which define the types of detectors, requirements for them and standard indicators that the distance between fire detectors must comply with.

Main normative document in this area are NPB 88-2001, approved by order of the GUGPS 04.06.01, which define the norms and rules for the design of fire extinguishing installations and alarm devices.

It is also necessary to take into account the Code of Rules 5.12.130.2009 dated March 25, 2009, dedicated to the rules and regulations for the installation of automatic fire extinguishing systems, taking into account subsequent changes, in which the rules for installing fire alarm sensors are set out taking into account the characteristics of various ceilings.

All current standards and requirements are aimed at ensuring a high level of fire safety and maximum effective use fire fighting equipment.

The disadvantage of these documents is their theoretical nature, i.e. they contain only a list of requirements. For practical use, various European standards are often used, which describe the nature of the ongoing processes of combustion and fire extinguishing from the point of view of their physical nature. Thus, the British standard BS 5839 allows you to simulate different stages of a fire and choose a solution for each specific situation.

Rules for placing smoke devices

There are several different types smoke detectors, which are installed in various rooms, and for which special rules apply for measuring the distance between them or from the wall to the detector.

• Optical point smoke devices are used in small-format objects, such as residential apartments and houses, hospital premises, and hotel rooms.
• Linear fire alarm installations are intended for spacious facilities such as warehouses, halls and halls public premises, airport or train terminals.
• aspiration detectors are installed in rooms cluttered with documents and materials, for example, in libraries, museum storerooms, and archives.

For reliable operation point and aspiration devices require fixed fixation under the ceilings, i.e. where the possibility of vibration is minimal.

The coverage area of ​​one detector depends on the ceiling height:

• up to 3.5 meters – 85 m2;
• from 3.5 to 12 meters – 55 m2;
• over 12 meters - a two-level placement is required (on the walls and ceiling) and the simultaneous use of point and linear models.

The distance between fire alarm devices should not exceed 9 meters.

Linear devices are placed on walls opposite each other at a distance of 9 meters. For high rooms (from 12 to 18 meters), two rows of sensors are used and the minimum distance between levels is at least 2 meters, with the bottom row located above 4 meters from the floor level, and the top row no closer than 40 cm from the ceiling.

At suspended ceilings smoke detectors are installed between two ceilings and directed to the ventilation exits.

Installation of flame detectors

The main requirement affecting the placement of fire flame detectors is the mandatory optical accessibility of the territory, i.e. the absence of obstacles that interfere with the fixation of the resulting flame.

The devices are mounted indoors and outdoors, they can be installed on the ceiling, wall or on equipment. For installation, the distance is measured not between fire detectors, but from the device to the corners. This indicator has limited limits:

• 10 cm for ceiling mounts
• 30 cm for wall appliances.

Also, it is recommended to set the placement of sensors from each other in a rectangular room according to the following parameters:

Placement of thermal linear detectors

Thermal linear detectors respond to temperature fluctuations. They are manufactured in the form of a thermal cable, sensitive along the entire length. The distance between fire alarm sensors inside buildings is 10-12 meters. When installing outside buildings (under canopies), installation rules require that a distance from the canopy to the cable be maintained at least 50 cm.

Heating devices are used in rooms with a large area and high ceilings, for example, in stadiums, inside warehouses, and production workshops.

The main requirement is reliable fixation to the wall, ceiling or good tension without fastening, so that fire safety networks are not at risk of damage. All laid cables are connected at the location of the control point, where all information about the fire threat is sent.

Placement of hand-held devices

Manual sensors are activated directly by a person, so the placement of fire detectors is determined by ease of access to them.

They are installed on the walls of the room at a height of about one and a half meters from the floor, i.e. inaccessible to accidental inclusion by animals or children, and located at the level of vision of most people.

Installation requirements are the absence of furniture or equipment blocking access to hand-held devices. Places for installing sensors must be publicly accessible and not have individual locks - stairs, corridors, halls. The distance between installation points should not exceed 50 meters, and, if external territories are controlled, then 150 meters.

"Note!

It also takes into account the distance to the lamp and its power, which affects the level of illumination of control points.”

Gas detector placement

When using a fire detector, the main indicator is the physical characteristics of the gas and the room itself, i.e. the probable directions and speed of gas propagation are taken into account. Typically, gas appliances are placed directly next to gas appliances with toxic or flammable gaseous substances, from which leakage is possible. Objects where it is decided to install gas fire detectors are industrial premises or special gas distribution points.

Placement of autonomous detectors

The peculiarity that an autonomous fire detector has is that it activates independently and does not require human presence or control. Place of use - residential premises, hotel rooms, sanatoriums, holiday homes and so on.

The standard area under the control of the device is 30 square meters, and if the space or ceiling plane has complex geometry, then this indicator must be reduced by a quarter, i.e. up to 23-25 ​​meters. Taking into account the characteristics of typical protected objects, devices can be installed one per unit area.

For reliable operation of the equipment, avoid direct exposure to the sun, as well as closed corners with unreliable ventilation.

The rules provide ceiling installation, and if this is not possible, the installation standards for wall fire detectors provide for a distance from the ceiling ranging from 10 to 30 cm.

Installation of light, sound and voice alarms

In addition to detectors that transmit information to control panels, various sirens are widely used, i.e. devices that convey alarm signals and fire information to all people in the danger zone. The main task of this equipment is to notify people of the need to evacuate when sensors detect fires (smoke, flame, jump in thermal level).

Annunciators transmit signals using:

• light indication,
• voice (speech) alerts,
• sound signals (sirens, bells).

Each type has its own requirements.

Light indicators require a place accessible for viewing, and a maximum distance of 60 meters between the nearest panels.

Sound and speech devices can be installed both indoors and outdoors, and are located at a height of about 2 meters from the floor.

Distance between alarm loops

Fire alarm loops are designed to transmit signals from the sensor location to the control point or the location of the siren.

Requirements for installing loops - the ability to convey information to the end point. Those. they must be protected from open flames or high temperatures.

Installation limitation - the distance to electrical cables is at least 50 cm, and in exceptional cases - 30 cm is allowed. This requirement is due to the following reasons:

• preventing accidental activation of the fire system;
• protection against damage when the electrical network is shorted.

The installation standards for fire detectors are mandatory for use. They ensure maximum equipment efficiency and create conditions for fire safety.

12. Fire alarm systems

General provisions when choosing types of fire detectors for the protected object

12.1. It is recommended that the type of point smoke detector be selected according to its ability to detect Various types fumes, which can be determined according to GOST R 50898.

12.2. Fire flame detectors should be used if an open flame is expected to appear in the control area in the event of a fire at its initial stage.

12.3. The spectral sensitivity of the flame detector must correspond to the emission spectrum of the flame of combustible materials located in the detector control zone.

12.4. Thermal fire detectors should be used if significant heat generation is expected in the control zone in the event of a fire at its initial stage.

12.5. Differential and maximum-differential thermal fire detectors should be used to detect the source of a fire if there are no temperature changes in the control area that are not related to the occurrence of a fire that could cause the activation of fire detectors of these types.

Maximum thermal fire detectorsnot recommended for indoor use:

with low temperatures (below 0 o C);

with storage of material and cultural values.

Note.Except in cases where the use of other detectors is impossible or impractical.

12.6. When choosing thermal fire detectors, it should be taken into account that the response temperature of maximum and maximum differential detectors must be at least 20° C above the maximum permissible indoor air temperature.

12.7. Gas fire detectors are recommended to be used if in the control zone, in the event of a fire at its initial stage, the release of a certain type of gases in concentrations that can cause the detectors to operate is expected. Gas fire detectors should not be used in rooms where, in the absence of a fire, gases may appear in concentrations that cause the detectors to operate.

12.8. IN in that case When the dominant fire factor in the control zone is not determined, it is recommended to use a combination of fire detectors that respond to various fire factors, or combined fire detectors.

12.9. It is recommended to select the types of fire detectors depending on the purpose of the protected premises and the type of combustible load in accordance with Appendix 12.

12.10. Fire detectors should be used in accordance with the requirements state standards, fire standardssecurity,technicaldocumentation and taking into account climatic, mechanical, electromagnetic and other influences at their locations.

12.11. Fire detectors designed to provide notification forAUP controls, smoke removal, fire warnings, mustbe resistant to electromagnetic interferencewith a degree of hardness not lower than second according to NPB 57-97.

12.12. Smoke fire detectors, powered by a fire alarm loop and having a built-in sounder, are recommended to be used for prompt, local notification and determination of the location of a fire in premises in which the following conditions are simultaneously met:

The main factor in the occurrence of a fire in the initial stage is the appearance of smoke;

There may be people present in protected areas.

Such detectors must be included in a unified fire alarm system with alarm messages output to the fire alarm control panel located in the premises of the duty personnel.

Notes:

1. These detectors are recommended for use in hotels, medical institutions, exhibition halls of museums, art galleries, library reading rooms, retail premises, and computer centers.

2.ApplicationThese detectors do not exclude equipping the building with a warning system in accordance with NPB 104.

Requirements for the organization of fire alarm control zones

12.13. It is allowed to equip a control zone with one fire alarm loop with fire detectors that do not have an address, including:

premises located on different floors, with a total area of ​​300 m2 2 or less;

up to ten isolated and adjacent rooms, with a total area of ​​no more than 1600 m 2 located on one floor of the building, while isolated rooms must have access to a common corridor, hall, vestibule, etc.;

up to twenty isolated and adjacent rooms, with a total area of ​​no more than 1600 m 2 located on one floor of the building, while isolated rooms must have access to a common corridor, hall, vestibule, etc., with a remote light alarm indicating the activation of fire detectors above the entrance to each controlled room.

12.14. The maximum number and area of ​​premises protected by one ring or radial loop with addressablefire detectors, determined by technical capabilities control and control equipment, technical characteristics of the detectors included in the loop and does not depend on the location of the premises in the building.

Placement of fire detectors

12.15. The number of automatic fire detectors is determined by the need to detect fires across the entire controlled area of ​​premises (zones), and for flame detectors - also equipment.

12.16. At least two fire detectors should be installed in each protected room.

12.17. In the protected area it is allowed to install onefire detector if the following conditions are simultaneously met:

a) the area of ​​the room is no more than the area protected by the fire detector specified in the technical documentation for it, and no more than the average area indicated in tables 5, 8;

b) automatic monitoring of the fire detector’s performance is ensured, confirming the performance of its functions and issuing a notification of a malfunction to the control panel;

c) identification of a faulty detector by the control panel is ensured;

d) the signal from the fire detector does not generate a signal to start the control equipment that turns on automatic fire extinguishing or smoke removal systems or fire warning systems of the 5th type according to NPB 104.

12.18. Point fire detectors, in addition to flame detectors, should be installed, as a rule, under the ceiling. If it is not possible to install detectors directly under the ceiling, they can be installed on walls, columns and other load-bearing building structures, as well as mounted on cables.

When installing point fire detectors under the ceiling, they should be placed at a distance from the walls of at least 0.1 m.

When installing point fire detectors on walls, special fittings or fastening on cables, they should be placed at a distance of at least 0.1 m from the walls and at a distance of 0.1 to 0.3 m from the ceiling, including the dimensions of the detector.

When hanging detectors on a cable, their stable position and orientation in space must be ensured.

12.19. The placement of point heat and smoke fire detectors should be made taking into account the air flows in the protected room caused by the supply or exhaust ventilation, while the distance from the detector to vent must be at least 1 m.

12.20. Point smoke and heat fire detectors should be installed in each ceiling compartment with a width of 0.75 m or more, limited by building structures (beams, purlins, slab ribs, etc.) protruding from the ceiling at a distance of more than 0.4 m.

If building structures protrude from the ceiling at a distance of more than 0.4 m, and the compartments they form are less than 0.75 m in width, the area controlled by fire detectors, indicated in tables 5, 8, is reduced by 40%.

If there are protruding parts on the ceiling from 0.08 to 0.4 m, the area controlled by fire detectors, indicated in tables 5, 8, is reduced by 25%.

If there are boxes or technological platforms in the controlled room with a width of 0.75 m or more, having a solid structure, spaced along the lower mark from the ceiling at a distance of more than 0.4 m and at least 1.3 m from the floor plane, it is necessary to additionally install under them fire detectors.

12.21. Point smoke and heat fire detectors should be installed in each compartment of the room formed by stacks of materials, racks, equipment and building structures, the upper edges of which are 0.6 m or less from the ceiling.

12.22. When installing point smoke fire detectors in rooms less than 3 m wide or under a raised floor or above a false ceiling and in other spaces less than 1.7 m high, the distance between the detectors indicated in Table 5 may be increased by 1.5 times.

12.23. Fire detectors installed under a false floor or above a false ceiling must be addressable or connected to independent fire alarm loops and it must be possible to determine their location.The design of the false floor and false ceiling must provide access to fire detectors for their maintenance.

12.24. Fire detectors should be installed in accordance with the requirements of the technical documentation for this detector.

12.25. In places where there is danger mechanical damage detector, a protective structure must be provided that does not interfere with its operation and the effectiveness of fire detection.

12.26. If different types of fire detectors are installed in one control zone,their placement is carried out in accordance with the requirements of these standards for each type of detector.

If combined (heat-smoke) fire detectors are used, they should be installed according to Table 8.

12.27. For rooms in which, in accordance with Appendix 12, it is possible to use both smoke and heatfire detectors, their combined use is allowed. In this case, the placement of detectors is carried out according to table 8.

Spot smoke detectors

12.28. The area controlled by one point smoke fire detector, as well as the maximum distance between the detectors and the detector and the wall, with the exception of the cases specified in clause 12.20, must be determined according to Table 5, but not exceeding the values ​​​​specified in technical conditions and passports for detectors.

Table 5

	Average area monitored one detector, m 2	Maximum distance, m
		between detectors	from the detector to the wall
Up to 3.5	Up to 85	9,0	4,5
St. 3.5 to 6.0	Up to 70	8,5	4,0
St. 6.0 to 10.0	Up to 65	8,0	4,0
St. 10.5 to 12.0	Up to 55	7,5	3,5

Linear smoke detectors

12.29. Emitter and receiverlinear smoke detectorshould be installed on walls, partitions, columns and other structures so that their optical axis passes at a distance of at least 0.1 m from the floor level.

12.30. Emitter and receiverA linear smoke fire detector should be placed on the building structures of the room in such a way that various objects do not fall into the detection zone of the fire detector during its operation. The distance between the emitter and the receiver is determined by the technical characteristics of the fire detector.

12.31. When monitoring a protected area with two or more linear smoke fire detectors, the maximum distance between their parallel optical axes, the optical axis and the wall, depending on the installation height of the fire detector blocks, should be determined from the table6.

Table 6

	Maximum distance between optical axes of detectors, m	Maximum distance from the optical axis of the detector to the wall, m
Up to 3.5	9,0	4,5
St. 3.5 to 6.0	8,5	4,0
St. 6.0 to 10.0	8,0	4,0
St. 10.0 to 12.0	7,5	3,5

12.32. In rooms with a height of over 12 and up to 18 m, detectors should, as a rule, be installed in two tiers, in accordance with Table 7, in this case:

the first tier of detectors should be located at a distance of 1.5-2 m from the upper fire load level, but not less than 4 m from the floor plane;

the second tier of detectors should be located at a distance of no more than 0.4 m from the ceiling level.

12.33. Detectors should be installed in such a way that the minimum distance from its optical axis to walls and surrounding objects is at least 0.5 m.

Table 7

Height of the protected room, m	Tier	Detector installation height, m	Maximum distance, m
			Between the optical axes of the LDPI	from the optical axis of the LDPI to the wall
St. 12.0 up to 18.0		1.5-2 from the fire load level, not less than 4 from the floor plane	7,5	3,5
		No more than 0.4 of the coating	7,5	3,5

Point heat fire detectors

12.34. The area controlled by one point thermal fire detector, as well as the maximum distance between the detectors and the detector and the wall, except for the cases specified in clause 12.30,

It is necessary to determine according to Table 8, but not exceeding the values ​​​​specified in the technical specifications and passports for detectors.

Table 8

Height Protected premises, m	Average area controlled by one detector, m 2	Maximum distance, m
		between detectors	from the detector to the wall
Up to 3.5	Up to 25	5,0	2,5
St. 3.5 to 6.0	Up to 20	4,5	2,0
St. 6.0 to 9.0	Up to 15	4,0	2,0

12.35. Point heat fire detectors should be located at a distance of at least 500 mm from heat-emitting lamps.

Linear thermal fire detectors

12.36. Linear thermal fire detectors (thermal cable) should, as a rule, be laid in direct contact with the fire load.

12.37. Linear thermal fire detectors may be installed under the ceiling above the fire load, in accordance with Table 8, while the values ​​of the values ​​indicated in the table should not exceed the corresponding values ​​of the values ​​specified in the manufacturer’s technical documentation.

The distance from the detector to the ceiling must be at least 15mm.

When storing materials on racks, it is allowed to lay detectors along the top of tiers and racks.

Flame detectors

12.38. Fire flame detectors must be installed on ceilings, walls and other building structures of buildings and structures, as well as on technological equipment.

Flame detectors must be placed taking into accounteliminating possible effects of optical interference.

12.39. Each point of the protected surface must be monitored by at least two flame detectors, and the location of the detectors must ensure control of the protected surface, as a rule, from opposite directions.

12.40.The area of ​​the room or equipment controlled by the flame detector should be determined based on the valueviewing angle of the detector and in accordance with its classaccording to NPB

72-98 (maximum detection range of a flammable material flame), specified in the technical documentation.

Manual call points

12.41. Manual fire call points should be installed on walls and structures at a height of 1.5 m from the ground or floor level.

Installation locations for manual fire call points are given in Appendix 13.12.42. Manual fire call points should be installed in places away from electromagnets, permanent magnets, and other devices, the influence of which may cause spontaneous operation of a manual fire call point.

(the requirement applies to manual fire call points, which are triggered when a magnetic contact is switched) at a distance:

no more than 50 m from each other inside buildings;

no more than 150 m from each other outside buildings;not less than 0.75m

There should be no various controls or objects in front of the detector that impede access to the detector.

12.43. The illumination at the installation site of the manual fire call point must be at least 50 lux.

Gas fire detectors.

12.44. Gas fire detectors should be installed indoors on the ceiling, walls and other building structures of buildings and structures in accordance with the operating instructions for these detectors and the recommendations of specialized organizations.

Fire alarm control and control devices, fire control devices. Equipment and its placementand taking into account climatic, mechanical, electromagneticand other impacts in the places where they are located.

12.46. Devices triggered by a signal automatic installation fire extinguishing or smoke removal or fire notification, must be resistant to external interference with a degree of severity not lower than the second according to NPB 57.

12.47. Reserve capacity of control panels (number of loops) designed to work with non-addressable fire detectors used in conjunction with automatic fire extinguishing installations, must be at least 10% when the number of loops is 10 or more.

12.48. Reception and control devices, as a rule, should be installed in a room with 24-hour presence of on-duty personnel. In justified cases, it is allowed to install these devices in premises without personnel on duty around the clock, while ensuring separate transmission of fire and malfunction notifications to the premises with personnel on duty around the clock, and ensuring control of notification transmission channels. In this case, the room where the devices are installed must be equipped with security and fire alarms and protected from unauthorized access.

12.49. Reception and control devices and control devicesshould be installed on walls, partitions and structures made of non-combustible materials. Installation of the specified equipment is allowed on structures made of flammable materials, provided that these structures are protectedsteelsheet with a thickness of at least 1 mm or other sheet non-combustible material with a thickness of at least 10 mm. In this case, the sheet material must protrude beyond the contour of the installed equipment by at least 100 mm.

12.50. The distance from the top edge of the control panel and control device to the ceiling alongrooms made of flammable materials must have at least 1m.

12.51. If several control panels and control devices are located adjacently, the distance between them must be at least 50 mm.

12.52. Reception and control devices and control devices should be placed in such a way that the height from the floor level to the operational controls of the said equipment is 0.8-1.5 m.

12.53. A fire station or a room with personnel on duty 24 hours a day should be located, as a rule, on the first or second floor. ground floor building. It is allowed to place the specified room above the first floor, and the exit from it must be in the lobby or corridor adjacent to the staircase, which has direct access to the outside of the building.

12.54. Distancefromdoors of a fire station or a room with personnel on duty 24 hours a day, up to staircase leading outwards should notusually exceed 25 m.

12.55. A fire station room or a room with personnel leading24-hour duty must have the following characteristics:

the area is usually at least 15 m 2 ;

air temperature within 18-25 °Cat a relative humidity of no more than 80%;

the presence of natural and artificial lighting, as well as emergency lighting, which must comply with SNiP 23.05-95;

room illumination:

in natural light - at least 100 lux;

from fluorescent lamps - at least 150 lux;

from incandescent lamps - at least 100 lux;

for emergency lighting - at least 50 lux;

the presence of natural or artificial ventilation in accordance with SNiP 2.04.05-91;

availability of telephone communication with the fire department of the facility or locality.

should not be installed rechargeable batteries backup power except sealed ones.

12.56. In the premises of duty personnel who are on duty around the clock, emergency lighting should turn on automatically when the main lighting is turned off.

Fire alarm loops. Connecting and supply lines for fire alarm systems and control equipment

12.57. The selection of wires and cables, methods of laying them for organizing fire alarm loops and connecting lines must be made in accordance with requirements of the PUE, SNiP 3.05.06-85, VSN 116-87, the requirements of this section and technical documentation for devices and equipment of the fire alarm system.

12.58. Fire alarm loops must be designed to ensure automatic monitoring of their integrity along their entire length.

12.59. Fire alarm loops should be made with independent wires and cables with copper conductors.

Fire alarm loops, as a rule, should be made with communication wires, if the technical documentation for fire alarm control devices does not provide for the use of special types of wires or cables.

12.60. Fire alarm loops radial type, as a rule, should be connected to fire control and control devices using junction boxes and cross-connections.

In cases where the fire alarm system is not intended to control automatic fire extinguishing installations, warning systems, smoke removal and other engineering systems fire safety of the facility, to connect radial type fire alarm loops with voltage up to 60 V to the reception and control devices, connecting lines made by telephone cables with copper conductors of the complex communication network of the facility can be used, provided that communication channels are allocated. In this case, dedicated free pairs from the cross-connection to the distribution boxes used when installing fire alarm loops, as a rule, should be placed in groups within each distribution box and mark with red paint.

In other cases, connecting lines for connecting radial-type fire alarm loops to fire alarm control panels should be made according toclause 12.58.

12.61.

Connecting lines made with telephone and control cables must have a reserve supply of cable cores and junction box terminals of at least 10%.

12.62. When installing a fire alarm system with fire alarm control and control devices with an information capacity of up to 20 loops, it is allowed to connect radial type fire alarm loops directly to the fire alarm control and control devices. 12.63. Fire alarm loops ring type should be carried out using independent wires and communication cables, with the beginning and end ring loop

must be connected to the appropriate terminals of the fire control panel.12.64. The diameter of the copper cores of wires and cables must bedetermined based on the permissible voltage drop, but not less

0.5 mm.12.65. Power supply lines for control panels and fire control devices, as well as connecting lines for controlling automatic fire extinguishing installations,smoke removal or warningshould be done with independent wires and cables. It is not allowed to lay them in transit through explosive and fire hazardous premises (areas). In justified cases, it is allowed to lay these lines through fire hazardous rooms (zones) in the voids of building structuresclass KO or fire-resistant wires and cables with cables and wires laid in steel pipes

12.66. The joint installation of fire alarm loops and connecting lines, control lines for automatic fire extinguishing and warning systems with a voltage of up to 60 V with lines of a voltage of 110 V or more in one box, pipe, harness, closed channel of a building structure or on one tray is not allowed.

Joint gasket specified lines allowed in different compartments of boxes and trays that have solid longitudinal partitions with a fire resistance limit of 0.25 hours made of non-combustible material.

12.67. In case of parallel open installation, the distance from fire alarm wires and cables with voltage up to 60 V to power and lighting cables must be at least 0.5 m.

It is allowed to lay the specified wires and cables at a distance of less than 0.5 m from power and lighting cables, provided they are shielded from electromagnetic interference.

It is allowed to reduce the distance to 0.25 m from wires and cables of fire alarm loops and connecting lines without interference protection to single lighting wires and control cables.

12.68. In rooms where electromagnetic fields and interference exceeds the level established by GOST 23511, fire alarm loops and connecting lines must be protected from interference.

12.69. If it is necessary to protect fire alarm loops and connecting lines from electromagnetic interference, shielded or unshielded wires and cables laid in metal pipes, boxes, etc. In this case, the shielding elements must be grounded.

12.70. External electrical wiring for fire alarm systems should generally be laid in the ground or in a sewer.

If it is impossible to lay them in the specified way, it is allowed to lay them on the outer walls of buildings and structures, under canopies, on cables or on supports between buildings outside streets and roads in accordance with the requirements of the PUE.

12.71. Mainand backup cable power supply lines for fire alarm systems should be laid along different routes, eliminating the possibility of their simultaneous failure during a fire at the controlled facility. The laying of such lines, as a rule, should be carried out through different cable structures.

Parallel laying of the specified lines along the walls of the premises is allowed with a distance between themin the light at least 1 m.

The joint laying of the specified cable lines is allowed, provided that at least one of them is laid in a box (pipe) made of non-combustible materials with a fire resistance limit of 0.75 hours.

12.72. It is advisable to divide fire alarm loops into sections using junction boxes.

At the end of the loop, it is recommended to provide a device that provides visual control of its on state (for example, a device with a flashing signal other than red with a flashing frequency of 0.1-0.3 Hz.),as well as a junction box or other switching device for connecting equipment for assessing the condition of the fire alarm system, which must be installed at an accessible location and height.

Requirements for the placement of fire detectors are given in NPB 88-2001* “Fire extinguishing and alarm installations. Design norms and rules." However, this document regulates only the basic options for placing detectors for relatively simple cases. In practice, there are often rooms with sloping ceilings, decorative suspended lattice ceilings, supply and exhaust ventilation etc., which must be properly protected, despite the lack of specific instructions in NPB 88-2001*. For all non-standard cases, there is a general requirement in clause 3. NPB 110-03 “List of buildings, structures, premises and equipment subject to protection by automatic fire extinguishing installations and automatic fire alarms”: “Type of automatic extinguishing installation, extinguishing method, type of fire extinguishing agents, type of plant equipment fire automatics determined by the design organization depending on the technological, structural and space-planning features of the protected buildings and premises, taking into account the requirements of current regulatory and technical documents.” NPB 88-2001* also contains General requirements, for example, according to clause 12.19, “the placement of point heat and smoke fire detectors should be made taking into account the air flows in the protected room caused by supply or exhaust ventilation,” however, criteria for optimizing the location of detectors are not given, it is only stated that “in this case, the distance from the detector there must be at least 1 m to the ventilation hole.”
You can avoid gross design errors in many complex cases by using Additional materials, for example, the European Standard BS 5839-1:2002 on Fire Detection and Alarm Systems for Buildings, Part 1: Code of Practice for the Design, Installation and Maintenance of Systems, where each section and paragraph first sets out the physical processes and then requirements arising from them, which allows you to be confident in the correctness of the chosen solution in a particular case. For example, when arranging automatic fire detectors, it is necessary to take into account the specifics of their operation depending on the type:
“The operation of heat and smoke detectors depends on convection, which carries hot gas and smoke from the fire to the detector. The location and installation step of these sensors should be based on the need to limit the time spent on this movement and provided there is a sufficient concentration of combustion products at the location of the sensor. Hot gas and smoke will generally concentrate in the highest parts of the room, so this is where heat and smoke detectors should be located. Since smoke and hot gases rise upward from the fireplace, they are diluted with clean and cold air, which enters the convective stream. Consequently, as the height of the room increases, the size of the fire rapidly increases, sufficient to activate heat or smoke sensors. To some extent this effect can be compensated for by using more sensitive sensors. Linear optical beam smoke detectors are less sensitive to the effect high ceiling than point-type sensors, since as the smoke-filled space increases, the length of the beam affected by smoke increases proportionally. In addition, when the convection jet captures the surrounding air, the gases are cooled. If the ceiling is high enough and ambient temperature in the upper part of the room is high, the temperature of the gas and smoke mixture can drop to a temperature environment at a level below the ceiling. This is possible if the indoor air temperature increases with altitude, for example as a result of solar heating the air at higher levels may be higher than the smoke temperature. A layer of smoke will then form at this level before reaching the ceiling, as if the room had an invisible ceiling at a certain height. This effect is known as stratification - stratification. In this case, both smoke and hot gases will not affect the sensors installed on the ceiling, regardless of their sensitivity. It is usually difficult to predict with enough high degree confidence level at which stratification will occur. This will depend on the convective heat output of the fire and on the temperature profile within the protected space during the fire, neither of which is known quantitatively. If sensors are installed at the expected stratification level and stratification does not occur or occurs at a higher level, detection can be dangerously late because a relatively narrow convection jet may bypass the sensors. Eventually, as the fire enlarges and more heat is generated, the convection current will overcome the thermal barrier and the ceiling-mounted sensors will be operational, albeit at a later stage of the fire than if no stratification had occurred. (However, a larger lesion will usually be detected if the ceiling height is greater.) Thus, in a high room in which stratification is likely, although additional sensors may be used for more low levels In hopes of detecting a stratified layer, ceiling-mounted sensors should always be used. Since the hot gas jet is relatively narrow, the radius of the control zone of additional detectors must be reduced. Although the above considerations apply for the normal protection of any area, local areas can be protected by additional fire detectors. For example, systems with thermal linear sensors may be particularly suitable for protecting power plant components or cable networks. When used for this purpose, the sensor should be installed as close as possible to the location where fire or overheating might occur, and it should be located above or in thermal contact with the protected installation.
For efficiency automatic system fire detection will be affected by obstacles between heat or smoke sensors and combustion products. It is important that heat and smoke detectors are not installed too close to obstructing the flow of hot gases and smoke to the detector. Near the junction of the wall and ceiling there is a “dead space” in which heat or smoke detection will not be effective. Since hot gas and smoke spread horizontally parallel to the ceiling, similarly there is a stagnant layer near the ceiling; This eliminates installation with the sensing element of a heat or smoke sensor located flush with the ceiling. This limitation may be less important in the case suction system, since this system actively draws air samples from a moving layer of smoke and hot gases. When installing heat and smoke sensors, the possible structure of air flows in the room should be considered. Air conditioning and ventilation systems with high level air exchange can adversely affect the sensors' abilities by creating an influx of fresh air and the outflow of heated air, smoke and gases from combustion or diluting smoke and hot gases from the hearth. Smoke detectors can be installed to monitor smoke in ventilation ducts. Basically, such sensors should help prevent the spread of smoke ventilation system, any recirculation must be stopped in case of fire. These sensors can be connected to the system fire alarm, but if smoke detectors have normal sensitivity, they cannot be a satisfactory means of detecting a fire in the area from which the air is supplied, since the smoke is diluted by the clean air extracted...”
From the above physical model, two basic principles emerge that are taken into account when placing smoke and heat fire detectors:
- when flat floors in the absence of interference and obstacles, smoke and heat detectors protect the area in the form of a circle in the horizontal plane;
– it is necessary to regulate the minimum and maximum distance of detectors from the ceiling.

Fig.1. The simplest scheme smoke and heat detector placement

According to BS 5839-1:2002, the radius of protection for smoke detectors is 7.5 m, for heat detectors - 5.3 m in horizontal projection. Thus, it is easy to determine the placement of detectors in a room of any shape: the distance from any point in the room to the nearest smoke IP in the horizontal projection should be no more than 7.5 m, from the thermal one - no more than 5.3 m. These radii of the protected area determine somewhat larger distances between detectors when arranged in a square grid (Fig. 1) compared to the requirements of NPB 88-2001*. Significant savings in the number of detectors (approximately 1.3 times) are achieved in large rooms when using arranging detectors in a triangular grid (Fig. 2).

Fig.2. Installation of detectors in large rooms

Currently, in practice, these provisions can only be applied when using aspirating detectors. The Recommendations of the Federal State Institution VNIIPO EMERCOM of Russia for the design of fire alarm systems using aspirating smoke fire detectors of the LASD and ASD series indicate that “when protecting rooms of arbitrary shape, the maximum distances between air intake openings and walls are determined based on the fact that the area protected by each air intake opening has the shape of a circle with a radius of 6.36 m (Fig. 3).

Fig.3. Each hole protects a circle with a radius of 6.36 m

Distance to ceiling
According to the British Standard BS5839, smoke detectors must be installed on the ceiling with their sensing elements located below the ceiling within:
1) 25 mm – 600 mm for smoke sensors;
2) 25 mm – 150 mm for thermal sensors.
A layer remains directly next to the ceiling clean air, which determines the minimum distance from the sensitive element of the smoke and heat detector to overlap equal to 25 mm. For the same reason, flush installation of detectors is prohibited. In NPB 88-2001*, such a requirement is indicated so far only for a linear smoke fire detector, clause 12.29. “the optical axis ran at a distance of at least 0.1 m from the ceiling level” and for linear thermal fire detectors, clause 12.37: “the distance from the detector to the ceiling must be at least 15 mm.” According to NPB 88-2001* clause 12.18* for all point fire detectors, “when hanging detectors on a cable, their stable position and orientation in space must be ensured. In this case, the distance from the ceiling to the bottom point of the detector should be no more than 0.3 m.” BS5839 specifies different maximum distances from the floor for a smoke sensor and for a heat sensor. Smoke detectors provide early detection fire, at the stage of smoldering materials, and it is possible to place it at a distance of about 300 mm from the ceiling even in the absence of a stratification effect. Unlike smoke detectors, heat detectors do not detect smoldering fires, and at the open fire stage there is a significant increase in temperature; accordingly, there is no stratification effect and an increase in the distance between the ceiling and the heat-sensitive element by more than 150 mm will lead to unacceptably late detection of the fire, i.e. . will make them practically inoperable.

Perforated ceilings
At airports, in large shopping centers etc. Decorative grilles are often used to cover ducts and cables located under the ceiling. For example, “Griiii” type ceilings. How should fire detectors be installed in this case? BS 5839-1:2002 states that sensors mounted on the main ceiling can be used to protect the area below a perforated false ceiling if the following conditions are simultaneously met:
1) the perforation area is more than 40% of any 1m x 1m ceiling section;
2) the minimum size of each perforation in any section is at least 10 mm;
3) the thickness of the false ceiling is no more than three times the minimum size of each perforation cell.
In all other cases, the sensors must be installed below the false ceiling, and if protection of the ceiling space is necessary, additional sensors must be installed on the main ceiling in the ceiling space.
When the above conditions are met, there is practically no division of the room into two spaces; smoke passes through the perforation of the false ceiling and is detected by detectors installed on the ceiling. These conditions are met with a large margin for the Grilyato type ceiling; for greater persuasiveness, it is recommended to consider it as a decorative lattice that creates virtually no obstacle to the spread of smoke.

Sloping floors
The absence in our standards of the concept of inclined, non-horizontal overlap can lead to serious design errors. The maximum permissible distance from the sensitive element of the detector to the overlap determines the criterion for assessing the horizontality of the overlap, without using any inclination angle values. If the difference in ceiling heights when using smoke detectors does not exceed 600 mm, then smoke accumulates in the upper part of the room and the ceiling is considered horizontal, regardless of the area of ​​the room. Similarly for heat detectors, if the height difference does not exceed 150 mm, the ceiling is also considered horizontal, regardless of the size of the room. With large differences in altitude, smoke with warm air flows up the slope towards the ridge and fills top part volume. In this case, the first row of fire detectors is installed along the ridge, and the remaining rows are installed parallel to the first slopes. It is possible to place detectors at a lower level, while the sensitive elements of the smoke detector should be located no lower than 600 mm from the top of the ceiling, and thermal elements no lower than 150 mm (Fig. 4).

Fig.4. Room protection with slopes at different angles BS 5839-1:2002

In addition, a sloping section of the ceiling, as a rule, increases the rate of rise of the flow of smoke and warm air towards the top, thus reducing the delay time before the detector is triggered. Accordingly, BS 5839-1:2002 allows an increase in the distance between detectors in the top row: for each degree of slope angle, the distance between detectors is allowed to increase by 1%, up to a maximum of 25%. If the floor slopes have different angles tilt, then the distance between the detectors installed along the ridge is selected based on the smaller value determined by the smaller angle of inclination (Fig. 4). IN in this example between detectors along the ridge it is allowed to increase by 18%, i.e. up to 12.39 m. The remaining detectors are installed based on the standard value of the radius of the protected area, equal to 7.5 m in horizontal projection. It is recommended to pay special attention when determining the location of the next rows of detectors in order to avoid gaps between the circles of detectors of different rows and different radii.
Of course, we cannot use these nuances in practice, but the criterion of inclined overlap is quite applicable. According to NPB 88-2001* clause 12.18*, already mentioned above, for all point fire detectors “<...>the distance from the ceiling to the bottom point of the detector should be no more than 0.3 m.” Thus, in a room 9 x 9 m with a height difference of about 0.6 m, it is possible to install a detector in the center of the room, and if greater difference heights, it is recommended to place it on a higher part of the ceiling. In this case, the requirement specified in clause 12.18* must be met: “When installing point fire detectors under the ceiling, they should be placed at a distance from the walls of at least 0.1 m.” Note that in BS 5839-1:2002 this distance for horizontal slabs is 0.5 m.
Similar to the requirements for point smoke detectors, the installation of linear smoke detectors in BS 5839-1:2002 requires a beam to horizontal distance of between 25mm and 600mm. In a room with a non-horizontal ceiling, i.e. when the difference in ceiling heights is more than 600 mm, it is necessary to protect the space along the roof ridge. In this case, according to BS 5839-1:2002, the distance between the optical axes linear detectors can also be increased by 1% for each degree of inclination up to a maximum of 25% (Figure 5).

Fig.5. Protecting a room with a sloping ceiling

In our practice, the distance between the optical axes not only cannot be reduced, but also can hardly be measured in a horizontal projection, since Table 6 of NPB 88-2001* indicates the maximum distances directly between the optical axes of detectors without taking into account their possible placement on an inclined overlap

Fig.6. Average room protection

Where linear smoke detectors cannot be installed below the ceiling, for example in atriums with glass domed roofs, BS 5839-1:2002 allows them to be located below 600mm from the ceiling. However, with such placement of detectors, the protected area is significantly reduced and amounts to up to 12.5% ​​of the installation height in each direction from the optical axis (Fig. 6.) Smoke diverges over a larger area with increasing height, therefore, it is more economical to install linear optical detectors at the maximum possible height. So, for example, when installed at a height of 4 m, for reliable detection of a source, the distance between the optical axes should be no more than 1 m, when installed at a height of 20 m, respectively, no more than 5 m.
Floors with beams
In large industrial premises there are usually beams of considerable height on the ceiling. In this case, the placement of detectors must be carried out in accordance with clause 12.20. NPB 88-2001*: “Point smoke and heat fire detectors should be installed in each ceiling compartment with a width of 0.75 m or more, limited by building structures (beams, purlins, slab ribs, etc.) protruding from the ceiling at a distance of more than 0.4 m. If building construction protrude from the ceiling at a distance of more than 0.4 m, and the compartments they form are less than 0.75 m in width, the area controlled by fire detectors, indicated in tables 5, 8, is reduced by 40%. If there are protruding parts on the ceiling from 0.08 to 0.4 m, the area controlled by fire detectors, indicated in tables 5, 8, is reduced by 25%.”
However, it is not indicated along which axes the distance between the detectors should be reduced. The beams prevent the spread of smoke in the transverse direction, and, therefore, it is necessary to reduce distances in this direction, ensuring a given reduction in the controlled area. It makes no sense to reduce the distances between detectors along the beams, since smoke spreads even faster between the beams, since the effect of limiting the space appears, as in a corridor, where the distances between detectors can be increased by 1.5 times.

Fig.7. Ceiling with beams, M - distance between detectors

BS 5839-1:2002 discusses two options in more detail: linear beams (Figure 7) and honeycombs (Figure 8).

Fig.8. Honeycomb ceiling

The requirements of BS 5839-1:2002 for permissible distances between detectors across beams depending on ceiling height and beam height are given in Table 1.
Table 1

For a honeycomb-shaped ceiling, depending on the ratio of the height of the beam and the width of the cell, fire detectors are installed either on the ceiling or on the beam (Table 2). Here the limit for the height of the beam is 600 mm (as opposed to our 400 mm), but the relative height of the beam is also taken into account - an additional limit, 10% of the height of the room.
table 2

Ceiling height H (rounded to the nearest integer), m	Beam height D	Maximum distance to the nearest smoke (heat) detector	Detector placement at W	Detector placement at W>4D
6m or less	Less than 10% H	Like a flat ceiling	On the bottom plane of the beams	On the ceiling
More than 6 m	Less than 10% H and 600mm or less	Like a flat ceiling	On the bottom plane of the beams	On the ceiling
More than 6 m	Less than 10% H and more than 600 mm	Like a flat ceiling	On the bottom plane of the beams	On the ceiling
3m or less	More than 10% H	4.5 m (3 m)	On the bottom plane of the beams	On the ceiling
4 m	More than 10% H	5.5 m (4 m)	On the bottom plane of the beams	On the ceiling
5 m	More than 10% H	6 m (4.5 m)	On the bottom plane of the beams	On the ceiling
>= 6 m	More than 10% H	6.6 m (5 m)	On the bottom plane of the beams	On the ceiling

Where, H – ceiling height; W – cell width; D – beam height.