Each year, in the UK, approximately 200 people die as a result of house fires. Investigations into house fires reveal that many battery-operated smoke alarms fail to sound, due to flat or disconnected batteries. Sometimes it’s simply because there are no batteries in the alarm. When we’re asleep, our sense of smell is useless, which is why so many fire-related deaths occur during the night.
Smoke alarm installations
Battery-operated smoke alarms are fine, so long as they’re tested regularly, and batteries are replaced promptly.
A smoke alarm installation is a far more reliable method of protection, but it’s vitally important that these alarms are fitted with back-up batteries. A house fire is often caused by an electrical fault, which should cut off the circuit.
If your alarm is backed up by alkaline batteries, they’ll need to be changed annually. Re-chargeable lithium batteries will last as long as the smoke alarm itself, which should be replaced after 10 years.
Optical smoke alarm
An optical (photo-electric) smoke alarm uses a photodiode to convert light into electrical current. An infrared LED pulses a beam of light into the sensor chamber. Any smoke particles that enter the chamber will cause the infrared light to scatter. The scattered light is picked up by the photodiode, which triggers the alarm.
Optical smoke alarms are very good at detecting slow-burning fires (for example, smouldering upholstery), which produce a lot of smoke before there are flames.
Ionisation smoke alarm
The ionisation smoke alarm is super-sensitive to fast-burning, flaming fires. A balanced electrical charge within the chamber will be disturbed by intruding particles, causing a change in electrical current. This change in current triggers the alarm.
A heat alarm does exactly what it says on the tin: it sounds when it detects dangerously high temperatures. This type of alarm is ideal for the kitchen, as it’s insensitive to smoke, and therefore won’t be going off every time the toast burns! If you were to rely on heat alarms, you’d need at least one in every room. Our advice, however, is not to rely on heat alarms, but to use them in conjunction with other types of fire alarm.
How many smoke alarms should you have?
Ideally, you’d have a fire alarm in every room of your house, except the bathroom, as water vapour tends to set them off. For the kitchen, a heat alarm is ideal. In bedrooms, living rooms, hallway and landing, we suggest a mixture of ionisation alarms and optical alarms. Next best thing to a device in every room is one on each floor – perhaps on the landing and in the hallway.
There’s a legal requirement for landlords to provide at least one smoke alarm on each floor of a rented property, as well as a carbon monoxide (CO) detector. And it’s now mandatory for new builds to have a fire alarm system installed.
To find out more about fire alarm installations, just give us a call on 01603 559 311.