Chapter 8: Fire Detection And Warning
260. A fire warning system allows occupants to be alerted and the emergency fire action plan to be implemented. It is important that an outbreak of fire in premises with sleeping accommodation should be detected at an early stage so that the occupants are alerted and the emergency fire action plan implemented as soon as possible. The longer a fire continues undetected, the greater the risk to the safety of occupants.
261. Individual flats, and small premises normally comprising of no more than two storeys should be provided with a fire alarm system (designed for dwellings) complying with the recommendations of BS 5839: Part 6 for Grade D Category LD2, comprising interlinked, mains-operated smoke and heat detectors (with battery back-up) connected to either a regularly used local lighting circuit, or to an entirely independent circuit to which no other electrical equipment is connected.
262. Small premises comprising of 3 storeys in height should be provided with a fire alarm system (designed for dwellings) complying with the recommendations of BS 5839: Part 6 for a Grade A Category LD2 system. It should incorporate control and indicating equipment complying with the recommendations of BS EN 54: Part 2 and comprise interlinked, mains-operated smoke and heat detectors (with battery back-up) connected to an entirely independent circuit to which no other electrical equipment is connected.
263. In larger premises, particularly those with more than one floor, an electrical fire warning system should be provided which can be activated by a person using a manual call point and automatically by means of automatic fire detectors. In large or complex premises, particularly those accommodating large numbers of people, a more sophisticated fire alarm system may be required.
264. Other than the domestic type systems described above, a fire detection and warning system designed, installed and maintained in accordance with the guidance in BS 5839: Part 1 for a category L2 system is likely to be appropriate for the majority of other sleeping accommodation premises. A category L2 system is a system designed for the protection of life and which has automatic detectors installed in escape routes and rooms adjoining escape routes.
265. Information on maintenance and testing of fire warning systems is in Chapter 4. Guidance on the design, installation and maintenance of fire detection and warning system is contained in BS 5839: Part 1.
266. Where automatic detection of fire is provided for life safety, the system will be designated as a category L system, within which there are subdivisions L1 to L5.
L5 is a system designed to achieve a specific fire safety objective
L4 is a system which provides warning of smoke within escape routes
L3 is a system designed to give a warning before escape routes are impassable
L2 is a system designed to give warning before escape routes are impassable but with enhanced coverage in specified areas
L1 is a system installed throughout all areas of the building
267. Manual call points, often known as ‘break-glass’ call points, enable a person who discovers a fire to operate the fire warning system and immediately raise the alarm to warn other people in the premises. Manual call points are normally positioned at exit doors. They should be conspicuous and positioned no higher than 1.4 m from the floor, but may be reduced to make accessible to wheelchair users. Building occupants should not have to travel more than 45 m to reach the nearest call point.
268. A hinged cover on the call point can be a deterrent where there is the potential for malicious operation or accidental damage. Hinged covers are particularly recommended for the public access parts of buildings.
Automatic Fire Detection
269. The choice of automatic fire detector type depends on the nature of the hazard and the balance between the speed of system response and the need to avoid false alarms. The common types of automatic fire detector are:
- Heat Detectors which operate when a fixed temperature is reached (and may also respond to abnormal rate of rise of temperature). Heat detectors have a good performance in types respect of false alarms but are not appropriate where the detection of smoke is required (such as in escape routes)
- Smoke Detectors which detect the presence of smoke (either ionisation or optical type). They give a speedier response to most fires than heat detectors but have greater potential to generate false alarms. (Smoke detectors within corridors and stairs should be the optical type)
- Combustion Gas Detectors which respond to the gases produced in a fire such as Carbon Monoxide. They can be sensitive to smouldering fires, respond to many fires faster than heat detectors and have a good false alarm performance in the presence of dust, steam and cigarette smoke
- Multi-sensor Detectors contain a combination of heat, smoke or combustion gas detection. These sensors enhance system performance and some types have a low potential for false alarm actuations
270. Sounders are provided to alert building occupants and should be capable of rousing them from sleep. The type of warning signal and sound level should be appropriate for the premises, the characteristic of the occupants, the fire action plan, and staffing arrangements. Automatic fire detectors with integral sounders may be appropriate for most premises to which this guide applies. Systems that incorporate a sounder base unit in each detector head can provide a more even and tolerable sound level throughout than the peak sound associated with the use of separate point sounders.
271. An appropriate sound level will vary with the nature of the premises, the fire action plan, and staffing arrangements. Although 65 dB(A) is appropriate throughout the building, when persons are asleep on the premises a sound level of 75 dB(A) will be needed at the bed-head in bedrooms.
272. Where there are or may be occupants with hearing impairment to the extent that the fire alarm sounders cannot be perceived, then it will be necessary to consider whether there is a need to provide tactile and/or visual alarm devices for those persons.
273. As an alternative to conventional sounders, a specially designed voice-alarm may be suitable for some premises. Voice alarm systems can provide significant benefits in terms of reduced response time and improved information.
274. A control and indicating panel provides facility for indication of fire or fault signals and manual controls such as silencing and resetting. Where a control and indicating panel is installed, it should be sited at a location which is appropriate both for staff and for the arriving Fire and Rescue Service.
275. The provision of a suitable fire detection and warning system should be accompanied by suitable staff training and resident awareness so that persons know how to operate the system and how to respond to system operation. A schematic plan should be displayed adjacent to the control panel to allow staff to quickly identify and locate the source of an actuation. If the fire warning system has detection zones, these zones should be shown on a zone plan in a simple and unambiguous way.
276. The building should be divided into detection zones so that the actuation can be located quickly. The allocation of detection zones needs to take into account the layout of the building and should facilitate the emergency fire action plan. Detection zoning should comply with the recommendation in BS 5839-1, and should not be determined purely for the convenience of the system installer.
277. An addressable fire warning system is one where individual detectors and call points can be identified at the control and indicating equipment. Addressable systems are of great advantage in some premises as they reduce the time taken to identify the location of a fire. Where an addressable system is installed, zone indication is also necessary.
278. Certain fire safety equipment is designed so that it operates when the fire warning system operates; examples are:
- automatic release of door hold-open devices
- automatic closure of self-closing doors which are fitted with swing free arms
- automatic opening facility disabled on swing doors with automatic opening
- electronically powered locks on doors returning to the unlocked position
- automatic opening of some exit doors
279. In entertainment areas where the sound pressure level of amplified music exceeds 80 dB(A) then the music should be muted automatically in response to fire alarm actuation.
280. If an automatic life safety fire suppression system is installed, the fire warning should actuate if the suppression system operates.
281. With remote monitoring, the actuation of the fire warning system causes a signal to be transmitted automatically to a remote alarm receiving centre ( ARC). On receipt of a signal, the ARC then calls the Fire and Rescue Service. The arrangements with an ARC may contain conditions such as call filtering if requested by the premises management.
282. There are standards and third party certification schemes for ARCs. Dutyholders with a system connected to an ARC may wish to assure themselves about the quality of their own arrangements.
Reducing False Alarms
283. False alarms from automatic fire detectors or manual call point activation are a major problem causing disruption to the running of premises and many unwanted calls to the Fire and Rescue Service. If frequent false alarms occur in the premises, members of staff may become complacent and may not respond correctly to a warning in the event of a real fire.
284. A record of system activations should be kept. Each false alarm should be investigated to try to establish the cause. Remedial action may be needed, such as re-positioning a detector head or changing a detector to a different type. A fire warning system should not be disabled: if it is posing a problem, specialist advice should be sought from a competent contractor.
285. Steps can be taken to discourage inappropriate or accidental call point use such as the provision of a protective hinged cover on the call point, with or without a tamper alarm. In cases where there is the potential for objects to collide with a call point, then side impact protection could be provided.
286. Where a call point is sited close to a green box or button for door control, the door control feature should be clearly signed, to avoid unintentional activation of the fire alarm.
287. Where a fire warning system is connected to an ARC, arrangements need to be in place to take the system off-line during tests or for notification of the ARC.
288. In premises that have no management presence, residents and tenants should be encouraged to notify the landlord or managing agent of false alarms that occur so that remedial action can be taken.
289. When a fire warning system needs to be replaced due to age or condition or because dutyholders wish to improve reliability or functionality, dutyholders should consider technological advances. A replacement fire warning system should be an addressable system, other than in small or simple layout premises where identification of actuation will be obvious. Dutyholders should also consider the benefit of incorporating multi-sensor detectors as part of a replacement system.
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