8 [ OPINION
Article By: Martyn Walley, National Technical Manager, Aico Ltd.
FIRE ALARMS: WHAT TO USE AND WHERE In the domestic Smoke Alarm sector there have traditionally been three alarm types: Optical, Heat and Ionisation. These different sensor types react best to certain fire types. As a result, specification and installation requires a good knowledge of BS5839 Part 6 (the British Standard for domestic smoke alarm installation) and Building Regulations, to ensure the best levels of detection for a property.
But changes are afoot! The new breed of Multi Sensors, which combine two traditional sensing elements in one alarm, are rising in popularity. What’s more, there’s a further alarm type to hit the market which combines fire detection with another life safety device - Carbon Monoxide (CO) detection. So what alarm type should you use and where? Let’s start with the best known alarm types. As the name might suggest, Optical Alarms essentially ‘look’ for smoke using a pulsed light beam in the sensing chamber. They are most effective at detecting smouldering fires with large particles, such as produced by burning furniture, and are less likely to react to the type of invisible smoke produced by cooking fumes; so are ideal for
circulation spaces such as hallways close to kitchens and landings as per BS 5839-6. A Heat Alarm doesn’t detect smoke at all, but instead reacts to temperatures of 58ºC, as per BS 5446, or over. A Heat Alarm should only be used in a kitchen or garage and only as part of a Fire Alarm system that also includes Smoke Alarms. Furthermore, all of the alarms within that system must be interconnected to meet British Standards. A solo Heat Alarm in a property is not an option. Ionisation Alarms use a small radioactive source to detect the invisible smoke particles given off by fast-flaming, clean burning fires such as bedding and clothing. Ionisation Alarms have mostly proven so popular because they have been around the longest (they were the first commercially available Smoke Alarms) so are the most familiar and generally are priced lower than other alarm types, making them the default alarm choice. However, with greater understanding of fire alarm types and a wider choice of alarms now available, Ionisation Alarms are slowly falling out of favour because they can be over sensitive to cooking fumes and are deemed old technology now. Generally, we’d recommend restricting their use to bedrooms. That seems very straightforward, but there are instances when it’s not immediately obvious which alarm type to use; for example, where do you place an alarm and what type of alarm in an open plan property? Fear not, Multi Sensor Fire Alarms are the next step in alarm technology development which remove this problem! A Multi-Sensor Fire Alarm uses both Optical and Heat sensors within the same alarm unit and interprets the signals to get a better understanding of what’s really
GO!PUBLIC : JUNE 2018
