The components of the system

The primary objective of BS 5839-1 is to ensure that automatic fire detection and fire alarm systems are reliable and that, when faults occur, system down time is minimized. Reliability, in this context, involves not just relative immunity to faults, but capability of performing the objective of giving early warning of fire to all occupants of the building.

In order to ensure that the components of the system are fit for this purpose, the code recommends the use of components, such as manual call points, detectors, control and indicating equipment, fire alarm devices and power supply equipment, that comply with the relevant product standards for these devices. Generally, the relevant product standards are European standards that it has been necessary, under the agreement within the European standards Forum, CEN, for the UK to adopt as national standards. These standards are published as various parts of BS EN 54.²¹

European standards for point heat and smoke detectors have existed since the 1970s; the latest versions are published as BS EN 54-5 and BS EN 54-7 respectively. In the case of BS EN 54-5, the standard defines eight classes of detector. For normal ambient temperatures, class A1 or A2 are appropriate, the former being more sensitive than the latter. The code recommends that, if the maximum ambient temperature in the protected area is 40 °C or above, class B–G detectors should be used as appropriate. These are detectors with a high temperature of operation, extending from the 69 °C–85 °C range in the case of class B detectors to a range of 144 °C–160 °C in the case of class G detectors.

Some of the European standards are much more recent and have either replaced an existing British Standard or are the first recognized standard for the product in question. For example, BS EN 54-3 is the first British Standard for audible fire alarm devices, BS EN 54-10 is

21 BS EN 54, Fire detection and fire alarm systems.

the first British Standard for flame detectors, while BS EN 54-20 is the first British Standard for aspirating smoke detectors. In contrast, BS EN 54-2 and BS EN 54-4 have replaced BS 5839-4, which was the British Standard for control and indicating equipment. BS EN 54-2 relates to the control and indicating equipment, while BS EN 54-4 deals with the power supply equipment.

One significant European standard has been published in the UK as BS EN 54-11, the product standard for manual call points, which replaced BS 5839-2. BS EN 54-11 recognizes two different types of manual call point, reflecting the different practices in manual call point design between the UK and a number of other European countries.

In the UK, a fundamental principle of manual call point design has always been that it should require only a single action (e.g. breaking a glass element) to operate the call point. Elsewhere in Europe, it has commonly been the practice that two actions are required (e.g. breaking a glass element and, thereafter, pushing a button). BS EN 54-11 refers to these ‘single action’ and ‘double action’ call points as type A and type B manual call points, respectively.

However, although the European product standard recognizes both types of manual call point, BS 5839-1 recommends that only the type A (‘single action’) manual call points should be used in the UK, continuing existing practice. Nevertheless, as discussed in Chapter 16, a variation, whereby a hinged cover is fitted to the manual call point, may be acceptable in certain circumstances in order to avoid malicious false alarms.

At the time the code was written, there was no British, European or international standard for carbon monoxide fire detectors, although work was being carried out to draft suitable standards. However, such devices are manufactured, and their use is increasing. The code recognized this and, until such time as a suitable British or European standard is published, a sensitivity level is recommended, namely that the detector should be capable of detection within 60 seconds if the carbon monoxide concentration exceeds 60 parts per million. In addition, the code recommends that the detector should be capable of responding to two smouldering fire tests from BS EN 54-7 if the manufacturer declares that the detector is only suitable for detecting smouldering fires. If the manufacturer claims that the detector is suitable for installation instead of a smoke detector, the code recommends that the detector should be capable of responding to a fast burning fire test defined in BS EN 54-7. This latter test is particularly difficult for carbon monoxide detectors to sense, and the more restricted application is likely to apply unless the carbon monoxide sensor is used simply as one sensor within a multi-sensor detector.

The components of the system

An international standard (ISO) for carbon monoxide detectors has been published as ISO 7240-6, but has not been adopted as a British Standard (BS ISO). Work on such a standard is in progress within the European standards forum (CEN). In the meantime, BS 5839-1 recommends that multi-sensor carbon monoxide and heat detectors should conform to BS ISO 7240-8.

In large networked systems, it is now quite common to use a PC as the user interface (e.g. in a security control room). PCs are often used to provide text information, which can include various instructions to operators, and sophisticated graphic displays to enable the location of the fire to be easily identified. However, the code points out that it is unlikely that a PC would meet the requirements of BS EN 54-2.

Accordingly, the code recommends that a PC should be considered purely as a supplementary form of indicating equipment and that there should be control and indicating equipment complying with BS EN 54-2 adjacent to it. The term adjacent is not defined (e.g. in terms of distance), but it is likely that, in the case of a security control room, conventional BS EN 54-2 equipment anywhere within the room would be acceptable for the purposes of satisfying this recommendation.

Since the code specifically recommends compliance with the standards referred to above, a failure to use equipment that complies with these relevant standards and/or the recommendations of this clause (clause 11) of the code would constitute a variation from the code, which would need agreement by all interested parties if the recommendations of the code are to be satisfied.

However, compliance with the code does not necessitate third-party certification of any of the products (though this is required under third party certification schemes for fire alarm contractors). Nevertheless, the commentary (against which, of course, systems should not be audited) does advocate the use of components having certification under a recognized product certification scheme. Such a scheme should comprise third-party certification of product conformity against a relevant standard, based on testing and continuous surveillance, together with assessment of the manufacturer’s quality assurance systems against BS EN ISO 9000.

The code also points out that, where there is no British, European or international standard, it is advisable that care is taken to ensure, as far as possible, that the components are fit for purpose. The code points out that third-party approval against an appropriate test standard may provide assurance of this. In this connection, BRE Certification are already able to ‘approve’ carbon monoxide fire detectors against their own approval procedures for these devices, which are based on

the requirements of BS EN 54-7 and published as Loss Prevention Standard LPS 1265 for carbon monoxide detectors, and as LPS 1274 for combined carbon monoxide and heat multi-sensor detectors. (As noted above, a BS ISO standard does, however, exist for the latter detectors.)

In the case of multi-sensor optical and heat detectors, BS 5839-1 offers a choice of standard, with which it is recommended these detectors conform. Firstly, they may simply meet the relevant European standards for heat and smoke detectors (BS EN 54-5 and BS EN 54-7 respectively). Alternatively, they may conform to an international standard, published in the UK as BS ISO 7240-15. As a final alternative, they may conform to a European fire insurers’ standard, CEA 4021.