EVASAFE FIRE SYSTEMS

FREQUENTLY ASKED QUESTIONS ABOUT FIRE ALARMS

• When is a fire alarm required in a building?
  ANS. Although it is often not a legal requirement, it may be considered that a fire alarm should be provided wherever more than a few people are employed; it is normally, in the UK at least, a legal requirement to have "a satisfactory means of warning in case of fire" (i.e. a fire alarm) for most offices, shops, railway premises, hotels and larger guest houses, factories and houses in multiple occupation (HMOs). There are other special categories of building that also have legal requirements.
• What is meant by "satisfactory"?
  ANS. Normally this means a system meeting the relevant national standards. In the UK these are BS5839 Part 1:1988 for systems in buildings, and various component parts should meet the relevant other parts of BS5839 - e.g. Control Panels should meet part 4 requirements. Anyone needing detailed information on fire alarm systems and components would be well advised to read these standards.
• How loud should a fire alarm be?
  ANS. Normally sufficiently loud to be heard clearly above any ambient noise. For normally quiet areas a minimum sound level of 65dBA is specified. For noisier areas, at least 5dBA above any ambient noise level, and for bedrooms where there are no permanent night staff to wake sleeping persons, the sound level should be 75dBA at the bed head. This normally means an alarm sounder/bell in each bedroom.
• Are smoke and heat detectors a requirement of a fire alarm?
  ANS. Not necessarily. For smaller premises a simple "manual" system is often adequate. However, where an early warning of fire is needed for the safety of life, automatic detectors should be used to complement the manual activation of an alarm. There are normally 3 levels of protection, type L3 is the protection of escape routes, type L2 is the protection of vulnerable areas, and type L1 is total coverage. In most cases smoke detectors will be required, except for areas such as kitchens where fumes are often produced, where heat detectors would normally be used.
  If detectors are required for the protection of property, there are two levels of protection, level P1 giving total coverage, and P2 where low risk areas are not covered.
  A special case is fire protection of computer centres, which has its own British Standard, BS6266, which offers much advice on fire protection in general, and fire detection in detail, for such areas.
• What are the requirements for cabling a fire alarm?
  ANS. Normally cabling must be fire resistant, assuming operation is needed during a fire. This can be achieved by using Fire resistant cables, e.g. MICC or FP200 types, or, by running pvc cables in conduit, or by being buried in walls etc. Mechanical protection is also needed in some cases, to give protection from impact, abrasion or attack by rodents. Cabling would normally meet the requirements of the IEE Wiring Regulations, 16th Edition (also known as BS7671:1992)
  It should also be noted that there are systems not requiring cables which use radio. These systems are much cheaper to install, but the equipment is much more expensive! They are sometimes the only type acceptable to a client where the site is historical, heritage, prestige etc. A mixed system of conventionally wired and radio is sometimes a more cost-effective solution, since often the less prestigious areas do not require a radio system.
• How is a building divided up - i.e. how is the location of any fire determined?
  ANS. Any but the smallest building will normally be divided into a number of zones, each of which will have a separate indication on the fire alarm panel. Zones should not normally exceed 2000 square metres in area, nor cover more than a single floor. Often systems will have more than the minimum number of zones in order to give a more precise location. There are also systems called Analogue Addressable systems, where each and every device (call point, smoke and heat detector etc.) can indicate its state and location. These are normally used in larger premises where the detailed information is of more use, and the extra cost of this type of equipment may be justified.
• How do I know that a system meets the required standard?
  ANS. Any competent installation company should be willing to issue a commissioning certificate showing that the system meets the required standards. This is obviously only of use for newly installed systems, but companies such as ours will readily inspect existing systems, and issue a report, or certificate if one is justified. However, in many instances, it may not be possible to adequately inspect a system to ensure it meets all present requirements, so there may be some provisos or exceptions listed on any certificate for previously installed systems.
• How often should an alarm be tested?
  ANS. Normally once a week, with a DIFFERENT device being tested every week - not the same call point next to the panel, as is often the case! Further inspections of the system are required after any fire, and at monthly, quarterly, annual and five yearly intervals. The quarterly, annual and five yearly inspections should be carried out by a competent company.
• Will my alarm work if the mains fail?
  ANS. In nearly all cases it should! However, unless the system has been checked for correct stand-by operation in the event of mains failure, this may not happen. Often the stand-by batteries have not been checked, and need replacement or topping up if of the wet variety, so that in the event of mains failure, the system would only work for a few minutes or less. Systems are intended to operate for at least 24 hours without a mains supply, and sometimes for up to 72 hours.
• Why do we get so many false alarms?
  ANS. Often so called "False" alarms are in fact strictly unwanted alarms, where the system is in fact operating correctly, but where, for instance, a smoke detector is being triggered by some-one making toast where they should not, or where, perhaps, a heat detector would be more appropriate. Although smokers may occasionally trigger smoke detectors, this is not common as most detectors have a built-in delay to prevent triggering by passing smokers. This may not function adequately in a dedicated smoking room though, due to the continued presence of smoke.
  In some cases smoke detectors have been fitted where fumes are sometimes emitted, such as engine or boiler rooms - in such cases a dramatic reduction in alarms can be achieved by changing the detectors to heat type.
  One possible cause of unwanted alarms from heat detectors is if they are placed directly above ovens in a kitchen, and when the oven door is opened, the rapidly increasing temperature causes the "Rate-of Rise" element of the detector to operate, whereas the normal operating temperature of the detector has not been reached.
  Another common reason for false alarms is dirty detectors, which makes some types very prone to operate intermittently - in many cases the dust etc. can be easily blown out, but in severe cases the detectors may need cleaning by the manufacturers. It is sometimes the case that detectors are placed in an air stream which causes rapid dust build-up - the answer there is to move them out of the air-stream if this is practicable.
  Where an analogue addressable system is in use, it is often possible to obtain a readout of the state of each detector, and so to arrange cleaning before they cause any problems. Sometimes on these systems dirty detectors will cause pre-alarm indications to be given initially, which also allows preventative action to be taken.
  
  
  
  
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