Fire Alarm Systems Explained: BS 5839 Part 1 – 2013
In 2013 British Standard BS 5839-1 (Fire detection and alarm systems for buildings) were re-written to incorporate many new practices and advancement in technology within the design, installation and servicing of fire systems.
There were numerous positive changes made, leading to new methods to help reduce and manage the number of false alarms, increasing flexibility of design, inclusion of new technologies and a strong emphasis on contractual processes.
The code of practice in BS 5839-1 has been developed in line with current national building regulations in respect of both new-build and existing non-domestic premises.
This entry level guide to the Standard aims to address some of the main issues concerning fire detection and fire alarm systems, in respect of general and design queries.
Why might I need a fire detection / fire alarm system for my premises?
National building regulations require fire detection and fire alarm systems to be installed in many buildings at the time of construction. In addition, legislation requires that, where necessary to safeguard relevant persons in case of fire, existing premises are equipped with “appropriate fire detection and fire alarm systems”.
Non-domestic premises include, inter alia, common places of work (e.g. shops, offices, factories and warehouses), hotels, schools, hospitals, places of assembly (e.g. cinemas, theatres and churches), residential care homes, shopping centres, etc. However, and it is important to note that the list is not exhaustive and that any “reference to particular types of premises does not necessarily mean that all such premises are required by law to have such systems installed”.
For any premises, and as a general rule, best practice in fire safety should always begin with a fire risk assessment, which has the additional benefit of determining whether a fire detection / fire alarm system is required and, if so, what type of system should be installed (For details on / to book a Fire Risk Assessment please call us on 0117 9748999).
What are fire detection and fire alarm systems?
There are many different types of fire detection / fire alarm system, ranging from the most basic, manually operated, stand-alone devices through to highly sophisticated, digitally controlled networks. It all depends on the size and nature of the premises to be protected. In the context of BS 5839-1, which also applies to extensions and alterations to existing systems, “the term fire detection and fire alarm systems includes systems that range from those comprising only one or two manual call points and sounders to complex networked systems that incorporate a large number of automatic fire detectors, manual call points and sounders, connected to numerous inter-communicating control and indicating panels”.
It should be noted that this part of BS 5839 does not cover systems whose primary function is to extinguish or control fire. Voice alarm systems, systems combining fire alarm functions with non-fire related ones, audible or visual way-guidance systems designed to complement the fire alarm function, and public emergency call systems (999 or 112) also fall outside the remit of this publication.
What is meant by “categories of system”?
There are three main categories of fire detection and fire alarm system, although it should be noted that these are not mutually exclusive. A comprehensive system installed with the principal objectives of protecting both life and property could incorporate elements from all three categories: M, L and P. In particular, when selecting the appropriate category of system for a particular premises: “Even in buildings with comprehensive fire detection, the provision of manual call points will still normally be of great value; people in the vicinity of a fire will normally be… able to raise the alarm by use of a manual call point”, which action could potentially be taken before the fire is detected automatically.
Category M: manually operated systems with no automatic fire detectors
Examples of the types of buildings that might install category M systems include non-residential places of work, e.g. offices, shops, factories and warehouses, and smaller non-residential places of assembly where members of the public are typically present during opening hours, e.g. cinemas, theatres, restaurants and leisure centres. This is not an exhaustive list and it may be that additional, automated elements have to be added to the fire detection / fire alarm system in order to satisfy specific insurance requirements, such as protecting the business assets and / or protecting against loss of business through fire.
Category L: automatic fire detection and fire alarm systems principally intended for the protection of life. These are divided into five sub-categories:
L1: systems installed throughout a building, to offer the earliest possible warning of fire and thus the longest possible time for all the occupants to escape.
Examples of premises that might adopt L1 systems include those with sleeping accommodation, i.e. hotels, hostels, hospitals and residential care homes, and larger, non-residential places of assembly such as covered shopping malls.
L2 and L3: systems installed only in defined parts of the building. The objective is to ensure that a fire warning is given early enough to enable occupants, “other than possibly those in the room of fire origin”, to escape safely before routes become impassable due to smoke, flames and / or toxic gases. L2 systems have the additional objective of giving early warning in specified areas of high fire hazard / risk, e.g. commercial kitchens and boiler rooms.
Examples of premises for which L2 or L3 systems might be appropriate are the same as for L1. Much will depend on the outcome / recommendations of the fire safety risk assessment, although L3 systems might be particularly suited to larger premises with a phased evacuation policy.
L4: systems installed in those parts of the escape routes comprising circulation areas, e.g. corridors and stairwells
L5: systems in which the protected area(s) and / or the location of detectors is designed to fulfil a specific objective in respect of fire safety other than those covered by categories L1–L4.
Examples of situations in which L4 or L5 systems might be appropriate, frequently coupled with category M elements, include those in which fire could rapidly spread from an unoccupied area of the building and thereby hinder escape from occupied areas. It is important to ensure that automatic fire detectors are positioned such that even cool smoke, which is typical of the early stages of a fire but stays lower to the ground than the hot smoke of a mature blaze, can reach and activate them, such that, for example, magnetic fire door holders are released and the fire doors
thereby closed. In other words, these automatic detectors must not be sited so high that the cool smoke passes below them and through the (still open) fire doors. Cool smoke is known as the “silent killer” as it can rapidly overcome the occupants of a building before its presence is even noticed, particularly in premises with sleeping accommodation.
Category P: automatic fire detection and fire alarm systems principally intended for the protection of property. These are sub-divided into the following categories:
P1: systems installed throughout all areas of the building, to offer the earliest possible warning of fire and thus the minimal amount of time between ignition and the arrival of the fire service.
P2: systems installed only in defined parts of the building
Examples of premises that might feature a category P system include those whose property insurer requires automatic fire detection for the policy to be valid. Although, by definition, such systems are geared towards the protection of property and are thus appropriate for unoccupied buildings, in some cases, e.g. if there is a security presence overnight, it may be useful to incorporate some manually operated elements into the system, i.e. M/P1 or M/P2
What are the main design considerations for an appropriate fire detection / fire alarm system?
Section 2 of BS 5839-1 covers the various aspects of the design process. It starts from the definition of the system category that is most appropriate for a particular building and its fire safety requirements and concludes with electrical safety.
What follows is an indication of some of the main points to consider.
We have already looked at relating automatic system categories to particular types of premises in the context of protection of life (L) or property (P), or a combination of the two, and noted that manual (M) systems frequently have a role to play in these. However, it is useful to bear in mind the that “the appropriate extent of automatic fire detection will normally be determined by a fire risk assessment, rather than a rigid application of a specific Category to every building of a specific type or occupancy” (For details on / to book a Fire Risk Assessment please call us on 0117 9748999).
It is important that system components, e.g. manual call points, detectors, CIE (control and indicating equipment) and other fire alarm devices, conform to relevant British Standards and have undergone type testing to these standards. Furthermore, it is advised that all components used have been certified under a recognized product certification scheme, i.e. third-party certification of product conformity to the relevant standard(s).
Monitoring, integrity and reliability of circuits external to control equipment
The design should limit the effect of faults in and / or work on the system. A fault (but not fire) signal needs to be given at the CIE in the event of any failure in the critical signal path, which comprises all the components and interconnections between every fire alarm initiation point (whether manual or automatic) and the input terminals of each fire alarm device.
Sub-division of a building into detection zones, which are typically protected by a number of manual call points and / or automatic detectors, is recommended for all but the smallest of premises. This is to ensure that those responding to the alarm are directed to the actual location of the fire and is a recommendation even for premises with addressable systems.
Many premises have a simple evacuation procedure in the event of fire: when a manual call point or automatic detector is activated, an alarm sounds throughout the building to tell everyone to leave. In some, more complex buildings, however, a phased evacuation policy might be in place, in which case separate alarm zones might be required. In such situations, it is recommended, inter alia, that the boundaries of every alarm zone (other than external walls) are of fire-resisting construction.
Communication with the fire and rescue service
In order to derive maximum benefit from the fire alarm / fire detection system, it is important that the emergency response services can be alerted as quickly as possible should fire break out. This can be achieved in a number of ways, depending on the category of system installed. In the case of manual systems, which rely on human intervention, a telephone call will suffice. Methods for automatic transmission are divided into four main categories: carrier systems, by means of normal telephone lines; cellular radio communication systems (public or private); private communication circuit systems between the protected premises and alarm receiving centre; and systems that use the public switched telephone network (“digital communicators”).
Audible alarm systems / visual alarm systems / alarm warnings for people with impaired hearing
It is essential that alarm signals are sufficient in nature and extent to warn all those for whom they are intended. In some situations, e.g. for occupants of a building who have a hearing impairment, it may be necessary to supplement the audible alarm with a visual one, although it is not normally recommended that only a visual alert is used. In premises with sleeping accommodation, e.g. residential care homes, additional, tactile devices, which can be placed under pillows or mattresses and are connected to the fire alarm system, may also be appropriate.
Manual call points
Manual call points need to be prominently sited, readily distinguishable from non-fire alarm call points, and distributed such that, from any point in the building, it is impossible to leave the storey or building itself without passing one. They must also be sufficient in number to ensure that the time between the discovery of a fire and the alarm being sounded is as short as possible.
Types of fire detector and their selection
Fire detectors a are designed to detect one or more of the four main components of a fire: heat; smoke; combustion gas (e.g. carbon monoxide); and infrared and / or ultraviolet radiation (i.e. flames). As their name suggests, multi-sensor fire detectors contain more than one sensor, each of which responds to a different physical and / or chemical characteristic of fire. The final choice of detector for a particular building will be governed by three main considerations: the speed of detection / response required, as determined by the fire risk assessment / fire safety a objectives; the need to minimize false alarms; and the nature of the fire hazard. Other issues such as cost and maintenance requirements may also be significant. It is important that all relevant factors are considered at the design stage as there is no one type of fire detector that is suitable for all applications.
NB The spacing and siting of fire automatic fire detectors is a context-dependent, technical matter for system designers.
Control and indicating equipment (CIE); networked systems
Three main functions are performed by centralized CIE: automatic monitoring and control of circuits external to the equipment and the supply of power to them; indication and location of fire / fault signals; and manual controls to enable actions such as routine testing and resetting of the system. Detailed recommendations apply to the siting of CIE and the facilities provided for (i) visual indication of fire signals and (ii) control of the system.
In respect of networked systems, the functions of the CIE are not centralized in one location, but are distributed amongst a number of “sub-panels” that are located remotely from each other and interconnected by means of a network that serves as a data highway. Some may act just as “data gathering” panels, while others can be fully functional control and indicating panels with a “stand alone” capability. This means they will continue to operate normally even if the communications link between the sub-panels fails.
The remainder of Section 2 on design considerations covers issues such as power supplies to the system; cables, wiring and other interconnections of the components in a system; radio-linked systems; and electromagnetic compatibility with other electronic equipment (e.g. mobile phones) in respect of both the design and installation. Electrical safety is in reference to technical information for the benefit of the designer and installer, with particular attention drawn to maintenance issues and the need to ensure the adequacy of earthing / protection against shock from exposed metal parts.
What are the main installation issues?
Many fire detection / fire alarm systems are highly complex and sophisticated, exhibiting and benefiting from the cutting edge of digital technology, and it is not within the remit of a basic guide such as this to debate the details of the installation process. Apart, perhaps, from the most basic of systems (e.g. one or two manually operated, stand-alone call points in a small, single-storey building), installation is a specialist undertaking and will vary according to the unique characteristics of a particular set of premises.
There are, however, two points of a general nature to note:
Firstly, it is important to ensure that, prior to the installation of a fire detection and fire alarm system, one organisation has accepted responsibility for compliance. BS 5839-1 emphasises this point because it is possible for more than one party to be involved in the process of design through to installation, commissioning and final handover: for example, following on from the fire safety risk assessment, an independent designer may work up the system specifications and then feed them through to another organisation, e.g. a specialist fire alarm or electrical installation contractor, which is to be responsible for supplying and installing the system; or, even in situations where the entire project from start to finish has been commissioned through a single, specialist contractor, the actual installation work could well be sub-contracted out.
Secondly, it is vital that the selection and siting of each of the fire alarm devices in a system, whether manual, automatic or a combination of both, are such that the possibility of false alarms is limited as much as possible: for example, smoke detectors should never be fitted in kitchens or bathrooms. As a general rule in respect of any design anomalies that may surface during installation of a fire
detection and fire alarm system, although the Standard makes it clear that, unless the installer is also the designer, “the identification of design shortcomings is not generally the responsibility of an installer”, best practice dictates that “if the installer is aware of such shortcomings, particularly those arising from features of the building that might not have been known to the designer, they be drawn to the attention of the designer, user or purchaser”.
What happens once the installation is complete?
Following installation there is the commissioning / handover of a fire detection and fire alarm system, which completes the process from initial survey and design through to final signing off of the system as fit for purpose. There are several stages in the post-installation phase, which can be summarised as follows:
The commissioning process involves the thorough testing of the installation to the recommendations of the Standard and to the designer’s requirements (i.e. system specification). The work must be carried out by a “competent person”, i.e. one who possesses the relevant current training, experience and capability to perform the task in accordance with all the relevant drawings and reference materials.
Part of the commissioning process involves ensuring that adequate records and all other relevant documentation have been provided to the end user or purchaser of the fire detection and fire alarm system. Of particular importance are accurate “as-fitted” drawings of the installed system and system-specific operation and maintenance manuals. Other requisite documentation includes: certificates for the design, installation and commissioning of the system; all relevant records, e.g. any agreed variations on the original system design specifications; and a logbook for recording all system events, e.g. fire alarm / fault signals, routine maintenance visits, etc.
Once a system has been commissioned, certificates must be issued for each of the three separate processes: design, installation and commissioning. Certification can be carried out by a single or multiple organisations but, in all cases, “it is essential that the person who signs these certificates is competent to verify whether the recommendations of this Standard in respect of the process to which the certificate refers have, or have not, been satisfied”.
Once the certification process has been satisfactorily completed, the system will be formally handed over to the user / purchaser. At this point, it is important that the organisation bearing contractual responsibility for the system issues a certificate of acceptance to the purchaser, for completion by them.
Once the final stages of handover, including certification, have been completed, responsibility for the day-to-day running and maintenance of the system passes to the management of the premises in which it has been installed.
Maintaining the system: what is involved?
No matter how technologically advanced a fire detection and fire alarm system might be with state-of-the-art self-monitoring and automatic fault detection features, there will always be the need for
human observation and intervention to ensure its continuous smooth running and optimum performance.
There are three main reasons for routine maintenance and testing:
1. To identify any faults signalled and take the appropriate action to rectify them;
2. To ensure there have been no major failures of the system, either as a whole or in part;
3. To familiarise occupants of the building with the fire alarm signal(s).
As such, it is important for the premises management to institute a schedule of system testing, which can be sub-divided into weekly, monthly and annual routines.
BS 5839-1 recommends the following in respect of weekly testing by the user:
1. The operation of a manual call point during normal working hours;
2. This test to be carried out at approximately the same time each week;
3. Additional tests to be made at least once a month for any employees not usually present during the normal weekly test;
4. In systems with multiple manual call points, a different one to be tested each week, so that all are eventually included in the schedule of testing over a period of time;
5. The routine test time should not normally exceed one minute, so that the occupants of the premises can learn to distinguish between this weekly alarm and an actual fire alarm.
In respect of voice alarm systems, the Standard recommends that these are tested weekly in accordance with BS 5839-8.
BS 5839-1 recommends the following in respect of monthly testing by the user:
1. If the standby power supply to the system includes an automatically started emergency generator, this should be tested monthly;
2. If the standby power supply is provided by vented batteries, these should be inspected visually. Furthermore all vented batteries and their connections should be examined on a quarterly basis (i.e. every three months) by a person competent in battery installation and maintenance technology.
Inspection and servicing
Over and above the weekly and monthly test routines, it is important for regular inspection and servicing of the system to be carried out, in order to identify and rectify any faults, including false alarm problems, and also to ensure that any changes made to the actual fabric of the building, e.g. extensions, alterations or remedial work, that might have been made in the meantime have not affected the system in any way, either through damage to any of its elements or by impacting on the level of protection it offers. Changes in use and / or occupancy levels of a building can also have a detrimental effect on the protection offered by existing fire protection and fire alarm systems so any such factors must also be taken into consideration during the inspection process. The recommended period between successive inspection and servicing visits should not exceed six months.
Because of the specialist nature of the work, inspections are usually contracted out to a fire alarm service organisation, whose competence can be assured by third-party certification (For details on / to book a Fire Alarm Service please call us on 0117 9748999).
Functions included in the periodic inspection and testing of the system include, inter alia, an examination of the logbook, to include follow-up action on any faults recorded, and a visual inspection of all the manual call points, automatic fire detectors and fire alarm devices, with particular regard to any changes in building structure, occupancy levels and / or use, as noted above.
In respect of non-routine attention to the system, there are several scenarios that can arise and to which the Standard applies detailed recommendations. These range, inter alia, from the appointment of a new servicing organisation (which will necessitate a special inspection of the system) through fault repair and system modifications to inspection and test of the system following any fire.
User’s responsibilities and premises management: who does what?
A fire detection and fire alarm system is designed to protect life and / or property. In order to fulfil this function, it is vital that maintenance, inspection and testing of the system are carried out on a regular, scheduled basis.
It is a complex process that can involve several different parties, so the Standard recommends that the system user appoints “a single, named member of the premises management to supervise all matters pertaining to the fire detection and fire alarm system”. This places responsibility firmly in the hands of one individual, whose role is “to ensure that the system is tested and maintained in accordance with the recommendations”.
These responsibilities include, inter alia: the keeping of appropriate system records and all relevant documentation; ensuring that all relevant occupants of the protected premises are aware of any specific role and / or responsibility assigned them in respect of the fire detection and fire alarm system; and that the system itself is protected from any development that might negatively impact on the standard of protection it offers and / or contribute to the incidence of false alarms.
The logbook is a key document and, as well as the details of the manager / supervisor to whom responsibility for the fire detection and fire alarm system has been delegated, should contain a record of all the events that concern the system, whether these occurrences were scheduled or not (e.g. routine maintenance visits, test signals, fault signals, etc.). This comprehensive information can be valuable to whoever services the system and might also provide evidence of compliance with certain aspects of fire safety legislation, should such need arise.
Information in this guide is given in good faith, but Cannon Fire and Security cannot be held responsible for any omissions or errors. The company reserves the right to change specifications of products at any time and without prior notice
For more information please visit www.cannonsecurity.co.uk, call 0117 974 8999 or email email@example.com
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