Fire alarm system: guidelines in codes of practice.
Designing any security system has its own characteristics. Perhaps the most demanding in terms of compliance with regulatory documentation are the automatic fire alarm system (AFS) and the fire alarm and evacuation management system (FOMS). When designing even a small facility, it is necessary to take into account all the rules and regulations, which are not immediately understandable.
Let's consider the most common questions that arise when designing these systems.
Let's assume that it is necessary to equip a 3-story administrative and utility building with an APS and SOUE with a total area of 600 m2.
According to SP 5.13130.2009 (set of rules 5.13130.2009 «Fire protection systems. Automatic fire alarm and fire extinguishing systems. Norms and design rules»), Appendix A, Table A1, we determine that this facility does not need to be equipped with an automatic fire extinguishing system.
According to SP3.13130.2009 (set of rules 3.13130.2009 «Fire protection systems. Alert system and evacuation control system for people in case of fire. Fire safety requirements»), section 7, table 2, we determine the required type of alert.
The first question that arises: in which rooms should fire alarms be installed? The answer to this is provided by SP5.13130.2009, Appendix A, paragraph 4:
In the buildings and structures specified in this list, all rooms, regardless of area, should be protected by appropriate automatic installations, except for the rooms:
with wet processes (showers, toilets, refrigerated chambers, washing rooms, etc.);
ventilation chambers (supply and exhaust, not serving production facilities of category A or B), water supply pumping stations, boiler rooms and other rooms for engineering equipment of the building, in which there are no flammable materials;
categories B4 and D for fire hazard;
stairwells.
It should be borne in mind that the premises listed as wet process premises sometimes require the installation of an APS. For example, a sink may be equipped with household appliances, the malfunction of which may cause a fire, and the vestibule adjacent to the bathroom and being part of it may contain furniture.
The question often arises: why does the stairwell not need to be equipped with an APS, but the vestibule leading to the street does? There are windows with curtains in the stairwells, there is also a smoking area, and the vestibule is empty and has bare concrete walls.
To avoid complications when handing over the facility to the fire inspector, detectors are always installed in the vestibules, unless there is confirmation that the vestibule is part of the stairwell. If there is something to burn in the stairwells, they are equipped with APS.
It happens that the project is carried out by one organization, and the installation and commissioning of the facility is carried out by another. The project can be commissioned based only on the explication of the premises, and not on their actual characteristics. The project does not indicate either curtains on the windows of the stairwells or carpeting in the bathrooms. But when it comes to commissioning the facility, it will be necessary to either change the characteristics of the premises or install detectors in them.
In administrative and domestic buildings, as in any other, there are sometimes small rooms without windows, which are often converted into cabinets and storage rooms. In fact, these rooms remain separate rooms and require the installation of an APS. In fact, these are cabinets with shelves along the entire depth. The shelves create a barrier to the spread of smoke, and under each of them you need to install a fire alarm (or even more than one, if the system is not addressable). A cabinet with alarms looks ridiculous, especially since you will have to move the things stored in it. To avoid this situation, it is necessary to dismantle the shelves, i.e. return the room to its original appearance, otherwise it will be difficult to put the facility into operation.
The question often arises: Should I equip the attic and basement with an APS and SOUE?
In SP5.13130.2009, Appendix A, paragraph 4, these premises are not listed, i.e. it is permitted not to equip them if they have categories B4 and D for fire hazard.
It would also be a good idea to mention in the project explanation that the attic is treated with a fire-retardant mixture, does not contain a fire load, and access to it is limited. The same applies to basements, except that they are not treated with a fire-retardant mixture. If things are rarely stored in attics (due to the inconvenience of storage), then basements, as a rule, are in a worse situation — they are usually littered with all sorts of junk that should not be there. In order not to equip basements and attics with APS and SOUE, you need to get an official document from the customer confirming that these premises are not used and do not contain a fire load.
Another important question: Should fire alarms be installed behind a suspended ceiling?
SP5.13130.2009, clause 13.3.16:
Detectors installed on the ceiling can be used to protect the space located below the perforated false ceiling if the following conditions are simultaneously met:
the perforation has a periodic structure and its area exceeds 40% of the surface;
the minimum size of each perforation in any section is not less than 10 mm;
the false ceiling thickness is no more than three times the minimum perforation cell size. If at least one of these requirements is not met, the detectors must be installed on the false ceiling in the main room, and if it is necessary to protect the space behind the suspended ceiling, additional detectors must be installed on the main ceiling.
SP5.13130.2009, Appendix A, Table 2, clause 11:
Spaces behind suspended ceilings and under double floors when laying air ducts, pipelines with insulation made of materials of flammability group G1–G4, as well as cables (wires) that do not spread combustion (NG) and have fire hazard code PRGP1 (according to [21]), including when they are laid together2):
2) 1 Cable structures, spaces behind suspended ceilings and under double floors shall not be equipped with automatic installations (except for paragraphs 1–3):
a) when laying cables (wires) in steel water and gas pipes or solid steel boxes with opening solid covers;
b) when laying pipelines and air ducts with non-combustible insulation;
c) when laying single cables (wires) of the NG type for power supply of lighting circuits;
d) when laying cables (wires) of the NG type with a total volume of flammable mass of less than 1.5 l per 1 m of cable line behind suspended ceilings made of materials of flammability groups NG and G1.
In this case, the APS is installed regardless of the distance between the ceiling and the suspended ceiling.
Installing detectors behind a suspended ceiling entails not only an increase in equipment and material costs, but also increases the labor intensity of installation. Sometimes the distance behind the suspended ceiling is so small that it is extremely inconvenient to install there. To avoid installing detectors in cases where the conditions listed in points a, b, c are not met, it is necessary to calculate the volume of combustible mass of the cable line and compare the obtained result with the standard indicator given in point d.Here the difficulty lies not in the calculation itself (although it is quite tedious), but in the initial data required for it — the number and brands of cables laid behind the suspended ceiling. In ideal conditions, this information, documented, is provided by the customer. In reality, the customer often cannot provide the information, and it is difficult for the contractor to clarify this issue during the survey.
The next question concerns cable lines: what should they be made of and what should they be laid with?
SP6.13130.2009 (Code of rules 6.13130.2009 «Fire protection systems. Electrical equipment. Fire safety requirements»), section 4, paragraph 1:
Cable lines of fire protection systems must be made of fire-resistant cables with copper conductors that do not spread combustion when laid in groups according to category A according to GOST R IEC 60332-3-22 with low smoke and gas emission (ng-LSFR) or do not contain halogens (ng-HFFR).
SP5.13130.2009, section 13, clause 15.3:
The selection of electrical wires and cables, methods of their installation for the organization of fire alarm loops and connecting lines must be made in accordance with the requirements of GOST R 53315, GOST R 53325, [7], the requirements of this section and the technical documentation for the devices and equipment of the fire alarm system.
SP5.13130.2009, section 13, clause 15.4:
Joint installation of fire alarm loops and connecting lines, control lines for automatic fire extinguishing and notification systems with a voltage of up to 60 V with lines with a voltage of 110 V or more in the same box, pipe, bundle, closed channel of a building structure or on the same tray is not permitted.
Joint laying of the specified lines is permitted in different sections of boxes and trays with solid longitudinal partitions with a fire resistance limit of 0.25 h made of non-combustible material.
SP5.13130.2009, section 13, clause 15.15:
When laying them in parallel open spaces, the distance from fire alarm wires and cables with a voltage of 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 that they are protected from electromagnetic interference.
It is allowed to reduce the distance to 0.25 m from the wires and cables of loops and connecting lines of fire alarms without protection from interference to single lighting wires and control cables.
SP6.13130.2009, section 4, clause 6:
Cable lines of warning and evacuation control systems (SOUE) and fire alarms involved in ensuring the evacuation of people in the event of a fire must remain operational under fire conditions for the time required for the complete evacuation of people to a safe zone.
In order not to calculate the time required for the complete evacuation of people to a safe zone, it is necessary to use cables with high fire resistance. For example, with the FRLS marking, which have a fire resistance of 180 minutes. This time will be more than enough for evacuation. It is worth adding that when designing, in addition to regulatory documentation, one should rely on logic, taking into account the worst conditions.