Smoke Alarms


Cheap may not be


cheerful By Neil Perdell, National Technical Manager for Aico Ltd M


any of you are likely to be aware of the issue that made national news earlier this year regarding domestic


ten year smoke alarms beeping as if they were low on battery power, despite being just a few years old. The smoke alarms were fitted as part of free home fire safety visits by the Fire and Rescue services in properties across many areas of the UK. Thousands of people have now complained about problems with these alarms. It doesn’t make for good reading and it


certainly doesn’t show the fire safety industry in a good light. But the real problem here isn’t one of public relations for the fire industry. It’s actually a very real, very serious issue of safety as residents often disable the alarms to stop the noise, leaving them completely unprotected if a fire should break out. At the time of writing there still hasn’t been


a public explanation for the alarms’ malfunction, although there has been talk about them not being cleaned regularly enough by residents or being affected by


18 Electrical Wholesaler July 2010


nicotine and other forms of contamination. Unfortunately, this whole episode raises


serious concerns over the quality of some of the alarms on the market. ‘Built down to a price rather than up to a high quality standard’ comes to mind and surely this is not an acceptable principle for a life safety product.


Quality products A misconception also exists that an alarm


manufactured to BS EN 14604: 2005 is an endorsement of the quality of the alarm and therefore all alarms produced to the standard are directly comparable. But conformance only means that it meets the criteria set down in the standard; this doesn’t necessarily mean that the product is of high quality. There are some major differences in the


alarm build and quality between manufacturers, mostly as result of building down to a price. Often a manufacturer has just done the bare amount of work needed to make the alarm meet the requirements of


the standard. Transients are often the cause of intermittent, random beeping and can even trigger fully fledged nuisance alarms. This problem can be minimised or even eliminated by careful circuit design that incorporates additional components to smooth out the transients. However, you are only likely to find them in a quality alarm because their inclusion requires a high degree of circuit design expertise and they also increase manufacturing costs which, in turn, increases the market price. The design and build of the sensor


chamber, particularly in optical alarms can have a significant effect on susceptibility to nuisance alarm. There has been some talk that the smaller the chamber, the more sensitive the device. There is some truth in this, but this benefit can be more than outweighed by the problem of dust contamination and the resulting false alarms that could be experienced if the design of the chamber is suspect. Is there an insect mesh in place to protect the chamber from insects and fibres that are the most common


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