Smoke Alarm Buying Guide
Which smoke alarms for which room?
Ionisation smoke alarms (stairwells, landings, offices):
The traditional smoke alarm containing a small amount of radioactive material. This alarm is best used for the detection of fast flaming fires. However, it can be quite sensitive and might give false alarms near kitchens. Best installed on landings and in offices (although the optical smoke alarms will work there as well)
Optical smoke alarm (also called photo-electric smoke alarm) (bedrooms, lounges, hallways, also: offices and landings):
A type of smoke alarm that ‘sees’ the smoke and is less prone to false alarms. It is also fast at detecting smouldering fires (cables, soft furnishings etc). Best near (not in) kitchens, hallways, bedrooms, living rooms (also landings and offices). Does not contain radioactivity. Not suitable for areas open to the elements and very dusty areas.
Heat alarms (kitchens, garages):
A sensor type that detects the rapid change of temperature in case of a fire. This alarm avoids false alarms altogether and can be installed in kitchens and garages. If the garage is unheated, there might be problems with condensation at very low temperatures. Heat alarms only cover small areas, so larger kitchens require several heat alarms.In the kitchen the heat alarm needs to be installed on the ceiling (as all smoke alarms do) about 1m from the cooker.
There are also combination alarms available (eg optical and heat), sometimes called multi-sensors. These combine the advantages of the other sensor technologies, achieving quick detection of fire while avoiding false alarms.
When selecting smoke alarms, make sure that the alarms are certified to the relevant British Standard (BS EN 14604:2005 for ionisation and optical smoke alarms, BS5446-1:2000 for battery operated heat alarms and BS5446-2:2003 for mains heat alarms)
A word about mains operated smoke alarms
Mains powered smoke alarms to BS5839 part 6 grade D contain a backup battery. This can be an alkaline backup battery which needs to be replaced every year or so. The alternative is a sealed-in ten year rechargeable lithium battery, which makes a battery change unnecessary over the life of the alarm. Of course, regular testing is still required. The choice of battery is entirely up to the customer, although we recommend rechargeable batteries if the alarms are not tested and maintained by the customer themselves (eg in rented premises) to avoid batteries being removed or batteries becoming flat without being replaced.
Mains smoke alarms can be fed with power either from the nearest light fitting or directly from the fuse box. We recommend power supply from the light fitting. This is more cost-effective, especially when retro-fitting, and it is less likely that the lighting circuit is disabled to stop the ‘nuisance’ of bleeping alarms should the backup battery run low etc.
Whilst mains smoke alarms give you peace of mind for many years without false alarms or defects, it is dangerous to assume that they work forever. Smoke and heat alarms should be replaced after ten years, as they then start to become unreliable.
You will typically find the following smoke alarm requirements:
- Domestic, owner-occupied housing: BS5839 part 6 Grade F
- Extensions of domestic, owner-occupied housing: BS5839 part 6 Grade D
- Small businesses, many let properties: BS5839 part 6 Grade D with additional Manual Break Points in circulation spaces and sometimes additional Grade F smoke or heat alarms within let flats.
What do the different Grades mean?
Mains-powered, interlinked smoke and heat alarms. These are usually powered with a cable from the nearest light fitting. To create an interlink (all alarms go off at the same time in the case of a fire) they either require cable connection between the units or a radio-interlink connection. In businesses and larger let properties, these are often combined with manual break points.
With the appearance of ten year sealed smoke alarm units with radio-interlink, these are becoming more acceptable as an alternative to mains-powered, interlinked smoke alarms. Radio-interlinked manual break points are also available. However, we still recommend you check with your Building Inspector (in case of extensions), Local Council (rented accommodation), Fire Service (business) to ensure these alternative alarms are acceptable.
Battery operated, free standing smoke and heat alarms. On their own, they are mainly designed for domestic, owner-occupied housing. However, F Grade alarms with radio-interlink (especially when provided with 10 year sealed lithium batteries) can sometimes be applied as if they were Grade D. Again we recommend that you check first with the relevant authority.
- LACoRS guide: Housing: Fire Safety Guidance on fire safety provisions for certain types of existing housing
- Local Government Group: Guidance for Fire safety in purpose-built blocks of flats
- Fire Risk Assessment Guides
- A guide to BS5839