Which alarm sensor goes where?
Fire alarms have different sensors to detect different fire types. Some alarm sensors react to heat and some to the physical smoke created by a fire. By fitting the right type of alarm sensor you will avoid nuisance alarms and get the best protection.
Alarms containing optical sensors use an infra-red beam to detect smoke. They detect smoke from slow, smouldering fires such as electrical fires and are less prone to false alarms from cooking fumes if fitted in the hallway next to kitchens.
Fit Optical Alarms in: Hallway, Landing, Living Room, Dining Room
Alarms containing heat sensors only detect changes in temperature using a thermistor. The trigger level is set to 58°C degrees. Ideal for kitchens as they won’t nuisance alarm from cooking fumes but should not be used in other areas of a property as they will not provide the speed of response required – smoke alarms should be used instead, see above for guidance.
Fit Heat Alarms in: Kitchen, Garage
Siting alarms correctly throughout a property is vital to ensure they provide life saving detection and respond as quickly as possible in the event of a fire or carbon monoxide leak.
Every property is different, but here are some basic rules to follow when considering siting:
Smoke and Heat Alarms
- Alarms should be sited on the ceiling, as centrally as possible within the room/area they are installed
- Site 300mm from walls and light fittings – this is to ensure that they are outside of any ‘dead air’ spaces that occur in corners and spaces where the airflow may be blocked
- There should be an alarm within 3m of every bedroom door to ensure audibility
- Alarms should be positioned between high risk rooms and bedrooms
- Alarms should not sited within bathrooms or too close to a bathroom door as steam/moisture can affect them
- There should be an alarm within 3m of each escape door
Other factors to consider:
- Where stairways are present site alarms on the flat ceilings at the top and bottom of the stairs – do not site on the sloped ceiling directly above the stairs
- Peaked and sloped ceilings – for smoke alarms site a maximum of 600mm vertically down from the apex, for heat alarms a maximum of 150mm vertically down from the apex
- Beams (where the depth of the beam is less than 10% of the room height) – site the alarm twice the depth of the beam or 500mm, whichever is less
- Beams (where the depth of the beam is more than 10% of the room height) – treat the beam as a wall and fit alarms on both sides of the beam, or if the beam is less than 600mm deep site an alarm on the underside of the beam
For further information, refer to BS 5839-6:2013
Carbon Monoxide Alarms
Carbon Monoxide or (CO), is a particularly insidious gas. It is a killer. The naked eye can’t see it, it does not smell, it has no taste.
When installing Carbon Monoxide alarms it’s important to note that there are different siting requirements depending upon if the alarm is being installed in the room with the fuel-burning appliance or not.
In a room with the fuel burning appliance:
- Alarms should be sited on the ceiling
- Should be fitted between 1m–3m from all potential sources of Carbon Monoxide
- Sited 300m from walls and light fittings – this is to ensure that they are outside of any ‘dead air’ spaces that occur in corners and spaces where the airflow may be blocked
- If the fuel burning appliance is in a confined space, for example a boiler room then the alarm should be sited on the ceiling just outside the room
In a room without a fuel burning appliance:
- Alarms should be sited at breathing height
- If installed within a bedroom, this could be at the height of the bedhead
For further information, refer to BS EN 50292:2013
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