Smoke Detectors

Work in progress. Feel free to add to it

Smoke alarms save lives and every household should have at least one.

There are different types of smoke detectors and different legal requirments to have them.

Basic detection

What Sort of System should I have?

The 3 basic types of system used in dwellings that are 3 stories or less, have a floor area of less than 200m2 and that are NOT Houses of Multiple Occupation are

Grade F

This is the most basic protection and consists of one or more battery powered detectors.

Pros - Easy and cheap to fit.

Cons - The batteries are often removed and not replaced, either due to false trips or low battery power.

Grade E

Mains powered interlinked detectors with no battery backup/standby power

Pros - There are no batteries to replace

Cons - They do not work in a power cut, occupiers can turn them off by turning their power supply off. Cost of installation

Grade D

Mains powered interlinked detectors with battery backup

Pros - Works in a powercut.

Cons - Batteries will still need to be replaced, cost of installation.

Legal Requirements and other recommendations

Whilst there is no legal requirement to have smoke alarms in older houses, houses built after (need to check date) were required to have grade D or E systems installed. Houses having some types of building work carried out (eg loft conversion, 2 storey extensions) are also required to have grade D or E systems.

Where to Locate Detectors

What rooms should they be in

In an ideal world, all rooms would have a detector for the fastest alert, giving extra valuable minutes to escape. The low cost of detectors makes this practical now.

One per floor is the next best option, and is popular. The detector is put somewhere central, in a corridor or open space, so it can detect fires in adjoining rooms as soon as possible.

Whereabouts in the room should they be

They need to be placed where normal air currents will reach them. Avoid putting them near corners, or in places where airlfow is hindered. On the ceiling well away from the edges is a good choice.

What type of detector

The type of detector used is a compromise between the ability to detect the type of fire that may occur and to eliminate false alarms. Heat detectors are used in garages, kichens and laundry/utility rooms to help eliminate false alarms and smoke detectors are used in circulation spaces and habital rooms.

Types of Smoke Detector

Ionisation

Ionisation smoke detectors are the cheapest available detectors. They are not particulary sensitive to smouldering fires and are better suited to fast flaming fires.

Optical

Optical smoke detectors are more sensitive to smouldering fires and are better used in the circulation spaces and bedrooms.

Dual sensors

Dual sensors that incorporate both ionisation and optical capabilities are available that give the superiour protection against all types of fire.

Types of Heat Detector

Fixed Temperature

Fixed temperature heat detectors operate when they reach a preselected temperature (often 58degC). These are the most common type of heat detector in use and would be used in areas where rapid temperature fluctuations may be experienced (eg a kitchen when cooking.)

Rate of Rise of Temperature

Rate of rise heat detectors operate when their temperature rises at an abnormally fast rate. These can operate at a lower temperature than the fixed temperature detectors. They would be used in places when combustable materials may be stored and a fast flaming fire may occur.