Difference between revisions of "Smoke Detectors"
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They need to be placed where normal air currents will reach them. Avoid putting them near corners, or in places where airflow is hindered. On the ceiling well away from the edges is a good choice. Don't put them too close to a ceiling fan, or dust buildup will hinder them. | They need to be placed where normal air currents will reach them. Avoid putting them near corners, or in places where airflow is hindered. On the ceiling well away from the edges is a good choice. Don't put them too close to a ceiling fan, or dust buildup will hinder them. | ||
| − | = | + | =Types 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. Smoke detectors alarm much faster than heat detectors, and are used in most rooms & circulation spaces. Heat detectors are used where false alarms could occur with smoke detectors, such as in garages, kichens and laundry/utility rooms. | |
| − | 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 | ||
==Types of Smoke Detector== | ==Types of Smoke Detector== | ||
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Ionisation smoke detectors are the cheapest available detectors. They're prone to false alarms though. These can be used through most of a house, but are much too sensitive for a kitchen, and don't like damp in a bathroom. | Ionisation smoke detectors are the cheapest available detectors. They're prone to false alarms though. These can be used through most of a house, but are much too sensitive for a kitchen, and don't like damp in a bathroom. | ||
| − | They are not particulary sensitive to smouldering fires and are better suited to fast flaming fires. OTOH they detect fires before any smoke is even visible. | + | They are not particulary sensitive to smouldering fires and are better suited to fast flaming fires. OTOH they detect often fires before any smoke is even visible. |
===Optical=== | ===Optical=== | ||
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==Carbon Monoxide Detectors== | ==Carbon Monoxide Detectors== | ||
| + | CO detectors are not suitable for use as part of a fire detection system. | ||
==Electrical Installation Guidelines== | ==Electrical Installation Guidelines== | ||
| + | 4 core cable. On cct with lights, not on own cct, so supply failure is immediately evident. | ||
| + | |||
| + | ==Maintenance== | ||
| + | Test regularly. Keeping a battery or 2 in stock makes replacement instant. | ||
Revision as of 00:17, 3 March 2011
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.
The least effective configuration is a single detector on the ceiling at the top of the stairs.
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 airflow is hindered. On the ceiling well away from the edges is a good choice. Don't put them too close to a ceiling fan, or dust buildup will hinder them.
Types 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. Smoke detectors alarm much faster than heat detectors, and are used in most rooms & circulation spaces. Heat detectors are used where false alarms could occur with smoke detectors, such as in garages, kichens and laundry/utility rooms.
Types of Smoke Detector
Ionisation
Ionisation smoke detectors are the cheapest available detectors. They're prone to false alarms though. These can be used through most of a house, but are much too sensitive for a kitchen, and don't like damp in a bathroom.
They are not particulary sensitive to smouldering fires and are better suited to fast flaming fires. OTOH they detect often fires before any smoke is even visible.
Optical
Optical smoke detectors detect light being scattered by smoke particles. They don't suffer the false alarms of ionisation types, but cost more.
They are more sensitive to smouldering fires and are better used in the circulation spaces and bedrooms.
Dual sensors
Ionisation and optical are each msot sensitive to different types of fires, so combining both in one alarm gives the best possible detection speed. They suffer a fair few false alarms though.
Types of Heat Detector
Where smoke detectors aren't suitable, heat detectors are the next best bet. These are suited to kitchens and boiler rooms. The downside is they only respond to large fires, and detection speed is thus slow compared to smoke alarms.
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.) The downside is that it takes a blaze to reach 58C.
Rate of Rise of Temperature
Rate of rise heat detectors were developed to address 2 of the shortcomings of fixed temperature heat detectors. They operate when their temperature rises at an abnormally fast rate, rather than at a fixed temperature. They can thus trigger sooner than a fixed temperature detector. They also are good for use in locations that can reach 58C in use, such as a small boiler room with a big boiler.
These detectors are good for kitchens, and where combustable materials are stored and a fast flaming fire can occur.
Carbon Monoxide Detectors
CO detectors are not suitable for use as part of a fire detection system.
Electrical Installation Guidelines
4 core cable. On cct with lights, not on own cct, so supply failure is immediately evident.
Maintenance
Test regularly. Keeping a battery or 2 in stock makes replacement instant.