Why Replace smoke alarms
Several reasons are provided to justify the replacement of smoke alarms after ten years.
The Minnesota Department of Public Safety cite a nationwide study undertaken by the Consumer Product Safety Commission (CPSC), which states that 97% of smoke alarms should still be functioning after one year, if supplied with power. After ten years it is 73%, whereas after 20 years, this figure stands at 54%. The study also indicated that 60% of the failures were due to flat or removed batteries or a disconnected power supply and the study offered possible reasons for this. Ageing alarms may experience sensitivity drifting, which may, in turn, result in an increased frequency of accidental activation and an increase in people removing the power supply. It was thought that newer alarms with a ‘hush’ feature may contribute to remedying this
An NFPA report cites a study undertaken by Canada’s Ontario Housing Corporation supporting the fact that 3% of smoke alarms will fail within one year. They also say that after 30 years, nearly all the alarms will have failed. They conclude that replacement after ten years, with roughly a 30% probability of failure, is an appropriate balance between safety and cost
The South Australian Metropolitan Fire Service state that smoke alarm technology has improved significantly since legislation was introduced (similar requirements to the 1992 UK ones were introduced in Australia in 1995) and replacing old smoke alarms is an ideal opportunity to upgrade smoke alarm systems. The Australian Standard for smoke alarms (AS 3786) specifies an effective life of 10 years, suggesting that after that time effectiveness may be compromised with accumulated dust, insects, airborne contaminants and corrosion of electrical circuitry
In the early 1990s, the US Consumer Product Safety Commission undertook an extensive study, called the National Smoke Detector Project, to examine smoke alarm ownership and operability. Some failures were found in smoke alarms, but there were no large or systematic problems identified with detector designs or manufacturing practices that cast any doubt on their long term reliability. However, a variety of component failures, corroded battery clips and deterioration and corrosion of the horn element contacts were found in a few smoke alarms
Other reports from New Zealand and Canada looked at operability of battery smoke alarms, but no further reports on the operability and longevity of mains-wired smoke alarms could be found
Testing Smoke Alarms
It should be noted that the regular testing of smoke alarms should help identify inoperability as testing a smoke alarm simulates smoke and does not simply test the power supply. This would indicate smoke alarm maintenance messages remain a priority. However, it was queried whether all smoke alarm test functions operate in this way, or whether some simply do test power supply, be it battery or mains-wired
The general view from UK based smoke alarm manufacturers reflects the findings elsewhere. With contaminants such as dust, insects, grease and nicotine, the smoke alarm chamber is susceptible to becoming excessively sensitive or insensitive. This may lead to either an increase in nuisance false alarms, or to eventually becoming unable to detect smoke. One manufacturer reports that contamination is extremely variable, but that field experience indicated that 10 years is a reasonable compromise
Conclusion
Evidence of smoke alarm longevity appears to be scarce and inconclusive. As with other electronic items, there will be failures in the units when they are produced and failures during their lifetime due to individual component faults. Similarly, as they get older more faults are likely to occur. Problems specific to smoke detectors include increased sensitivity
In all the work identified so far, none has specifically concentrated on the failure of smoke alarms when they age. Smoke alarms do fail but the rate at which they do has not been accurately determined or related to their age.
Despite there not being much research, it does seem appropriate to replace smoke alarms after ten years (in line with manufacturers advice), unless individual alarm testing suggests earlier replacement.
Smoke Alarms
Every year the fire and rescue service is called to over 600,000 fires which result in over 800 deaths and over 17,000 injuries. About 50,000 (140 a day) of these are in the home and kill nearly 500 and injure over 11,000, many which could have been prevented if people had an early warning and were able to get out in time. In fact you are twice as likely to die in a house fire that has no smoke alarm than a house that does.
Buying a smoke alarm could help save your home and the lives of you and your family.
What are smoke alarms?
Smoke alarms are self-contained devices that incorporate a means of detecting a fire (smoke detector) and giving a warning (alarm), usually a very loud beeping sound. They are about the size of a hand and are normally fitted to the ceiling. They can detect fires in their early stages and give you those precious minutes to enable you and your family to leave your house in safety.
What type of smoke alarms are available?
There are mainly four types of smoke alarm currently on the market – ionisation, optical (also described as photo electronic), heat and combined.
Ionisation: These are the cheapest and cost very little to purchase. They are very sensitive to small particles of smoke produced by fast flaming fires, such as paper and wood, and will detect this type of fire before the smoke gets too thick. They are marginally less sensitive to slow burning and smouldering fires which give off larger quantities of smoke before flaming occurs. They can also be too over-sensitive near kitchens.
Optical: These are more expensive but more effective at detecting larger particles of smoke produced by slow-burning fires, such as smouldering foam-filled upholstery and overheated PVC wiring. They are marginally less sensitive to fast flaming fires. Optical alarms can be installed near (not in) kitchens, as they are less likely than ionisation alarms to go off when toast is burned.
Heat Alarms: They detect the increase in temperature from a fire and are insensitive to smoke. They can therefore be installed in kitchens. They only cover a relatively small area of a room, so potentially several heat alarms need to be installed in a large kitchen.
Combined Optical Smoke and Heat Alarms: Combinations of optical and heat alarms in one unit to reduce false alarms while increasing the speed of detection.
Combined Smoke and Carbon Monoxide Alarms: Alarms that combine both smoke detection and CO alarm protection in one ceiling-mounted unit. This reduces costs and takes up less of your living space.
Each type looks similar and is powered either by a battery, or mains electricity (or a combination of both, with the battery being the backup for the mains power, which could be interrupted). Some are interlinked so that any smoke detected in one room can raise the alarm at all others. This interlink can be achieved at the least cost with radio-interlinked smoke alarms.
Most smoke alarms now have hush buttons, for use where false alarms can be a nuisance e.g. when cooking. The alarm lets you know it’s been silenced by “chirping” or by displaying a red light – while a real fire producing lots of smoke will set it off anyway. Another helpful technology is the ‘Sleep-Easy Function’ which allows you to silence the alarm if a low battery beep starts in the middle of the night.
In a standard smoke alarm, the battery will need to be replaced every 12 months. You can buy alarms fitted with sealed 10 year batteries. The advantage is that you don’t have to replace the battery every year.
Mains-powered alarms have to be installed in all new buildings and after a major refurb. Make sure that the chosen mains powered alarm has a battery back-up. These can be alkaline batteries (need annual changing) or the alarm can be supplied with re-chargeable lithium batteries, which will last the lifetime of the alarm. Mains alarms need to be installed by a qualified electrician.
Some people find their alarms are frequently set off when they are cooking or when the toast burns. An alarm installed inside the kitchen must be a heat alarm rather than a smoke alarm. Just outside a kitchen (eg in hall or dining room) an optical smoke alarm or, even better, a combined smoke and heat alarm should be installed, as these are less sensitive to false alarm.
Alarms can also come with an escape light. When the alarm sounds, the light comes on. The light can help you see your way out, and it is good for alerting people whose hearing is not perfect.
In addition, for people who are hard of hearing or deaf, there are smoke alarm systems for the deaf. When the alarm goes off, a pad below the pillow vibrates (if you are asleep), and a strobe light flashes – alerting you or waking you up instantly.
Which smoke alarm should I choose?
The general rule is quite easy
Kitchen and Garage: Heat Alarms
Landings: Ionisation smoke alarms or combined optical smoke and heat alarms
Bedrooms, living rooms and hallway: Optical smoke alarms or combined optical smoke and heat alarms.
Always buy an alarm which has been certified to the British or European Standard.
How many should I fit in my home?
The number of smoke alarms to fit in your home depends on your particular circumstances. Fires can start anywhere, so the more that are fitted, the higher the level of protection.
For maximum protection an alarm should be fitted in every room (except bathrooms) You should choose the type most suited to the risk in each room. For minimum protection the number to be fitted will depend on the type of home you live in:
If your home is on one floor, one smoke alarm, preferably of the optical type, may be enough to provide you with early warning of a fire.
If your home has more than one floor, at least one alarm should be fitted on each level. In this case a combination of optical and ionisation alarms, preferably interconnected, will give the best protection.
Do not fit an alarm in the bathroom, as steam may trigger the alarm.
Where do I fit my smoke alarms?
Smoke alarms are usually screwed onto the ceilings, although specialist sticky pads can be used, and should be fitted as close to the centre of the room as possible, but at least 30 centimetres (12 inches) away from any wall or light fitting. You should always make sure that your alarm is fitted in a place where it can be heard throughout your home – particularly when you are asleep.
If your home is on one level, you should fit the alarm in the hallway between the living and sleeping areas. If you have only one smoke alarm and two floors, put it where you can hear it when you are asleep – on the ceiling at the top of the stairs leading to the bedrooms.
If you have a TV or other large electrical appliance in your bedroom, you should fit a smoke alarm there.
Looking after your smoke alarm
Follow the manufacturer’s instructions – smoke alarms need very little maintenance. A few minutes of your time during the year will ensure that your alarm is working and could help save your life and the lives of your family. You should:
Test your smoke alarm when the clocks are changed and vacuum it gently using the soft brush attachment to remove dust from the sensors
Once a year change the battery (unless it’s a ten-year alarm)
After 10 years it’s best to get a whole new alarm.
Do you keep forgetting to check your smoke alarms, help is at hand. Let us remind you to check them here.
Where can I buy them?
We recommend you buy your smoke alarms from a reputable company such as Safelincs who are able to cater for all your fire safety needs with their extensive range of products.
Remember:
Buying and fitting smoke alarms, and ensuring they are carefully and properly maintained, could give you those precious few extra minutes in which to make your escape safely.
Plan an escape from your home in advance and talk about it with your family. If a fire occurs you may have to get out in the dark and difficult conditions. Escaping will be a lot easier it everyone knows where to go. Make sure your routes remain free of any obstructions and that there are no loose floor coverings that could trip you.
Always check the battery regularly, replacing it when necessary, and never remove it for other purposes.