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Why do we need to replace smoke alarms older than 10 years? |
Between Experts |
Date Entered: Sep 22, 2009
Last Update: Sep 23, 2009 - 6:38 PM |
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Smoke Alarms should be replaced after 10 years or when they become inoperable, whichever comes first. |
Mahendra Wijayasinghe |
Date Entered: Sep 23, 2009 |
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Thirty years or more have passed since smoke alarms were first introduced as a legislated requirement in most jurisdictions. This means that a significant number homes may have smoke alarms older than 10 years.
According to the National Fire Protection Association (NFPA): - Aging smoke alarms don't operate as efficiently and often are the source for nuisance alarms
- Older smoke alarms are estimated to have a 30 percent probability of failure within the first 10 years
Newer smoke alarms do better, but should be replaced after 10 years or when they become inoperable, whichever comes first.
Rationale for 10 year replacement
As electronic devices, alarms are subject to random failures. Product, installation and maintenance standards are used to assure products work as designed despite this. Part of the technical basis for the first alarm product standard was an assessment of expected failure rate, estimated at four per million hours of operation or one every 30 years.
Early field studies of alarm reliability, notably by Canada's Ontario Housing Corporation, confirm the essential accuracy of this estimate, restated as a 3 percent failure rate per year. This means a very small fraction of home smoke alarms will fail almost immediately, and 3 percent will fail by the end of the first year. After 30 years, nearly all the alarms will have failed.
Smoke alarm replacement is a value judgment. As only 3 percent of alarms are likely to fail in the first year, annual replacement would be very expensive; however, at 15 years, the chances are better than 50/50 that the alarm has failed, which is too big a risk to take. Given that manufacturers' warranties for early alarms typically ran out in 3 to5 years, it is likely that in 10 years there is roughly a 30 percent probability of failure before replacement, which balances safety and cost in a way that makes sense to the responsible technical committees.
If a 30 percent failure probability still seems too high, remember that replacement on a schedule is only a backup for replacement based on testing. A national study found that home smoke alarms, when they fail, tend to fail totally, as opposed to hard-to-detect creeping failure, such as a loss of sensitivity. Regular monthly testing helps determine alarm failure as well as a dead or missing battery. Replacing alarms after 10 years protects against the accumulated chance of failure, but monthly testing is still the first and best means of making sure alarms work.
The following key messages, tips and suggestions may be useful to municipal fire/emergency service departments in promoting the replacement of smoke alarms older than 10 years of age. Local hardware stores may also support a smoke alarm replacement program as they stand to gain from the increased sales.
- Benefits outweigh the costs and smoke alarms are required by law: Compared to what you can lose, a $10 to $15 smoke alarm is a relatively inexpensive form of life protection for you and your loved ones.
- Testing regularly: Alarms should be tested monthly by pushing the test button. Once a year, use a smouldering cotton string, cigarette or incense until the smoke makes the alarm sound. If the alarm is battery-powered and doesn't sound, replace it with a new battery and try again. If it's electrically connected to household circuits and doesn't sound, check the fuse and try again. In either case, if the alarm still isn't working, replace the entire unit.
- Find the age of smoke alarms: Newer models have the manufacturing date code on the back of the device printed in plain English. Older smoke alarms may have plain English or coded manufacture dates that may appear on the back of the device, on the face of the horn, in the battery compartment or on the top sensing chamber.
- Disposal of old smoke alarms: The ionization type smoke alarms contain the radioactive material Americium 241 (see sidebar). In response to stringent regulations in some jurisdictions, the major smoke alarm manufacturers have set up take-back programs to deal with these units in an environmentally-responsible manner. For example, consumers may send First Alert, BRK and Family Guard smoke alarms to: BRK Brands, 25 Spur Drive, El Paso, TX 79906, (800) 323-9005; www.firstalert.com. On the front of the package, write For Disposal. Up to five smoke alarms are accepted for free. Ship American Sensors and Dicon Smoke Alarms by surface mail to: Dicon Inc., 20 Steelcase Road West, Unit #3, Markham, Ontario L3R 1B2, Canada, (800) 387-4219. On the front of the package, write For Recycling, $0 Value. Consumers may also contact:
- Their local municipal recycling programs for specific instructions on disposing smoke alarms.
- The manufacturer to see if old smoke alarms can be returned. Most manufacturers will take back their own alarms and dispose of or recycle the components. If the smoke alarm has an alkaline or lithium battery, check the local community recycling program for disposal instructions.
- Upgrade to a newer model: Replacing smoke alarms after 10 years provides the opportunity to install more technologically-advanced models of smoke alarms. For example, there are wireless interconnected smoke alarms without the need for a major rewiring job. These new battery-operated alarms are connected by radio frequency -- when one alarm sounds, the others in the home will go off as well. Another option is to install Dual-Sensor Smoke Alarms, which have both the ionization and photoelectric sensors that can detect and sound an alarm in both fast-flaming and slow-smouldering fires.
- Extended life batteries for smoke alarm designed to eliminate the need for battery replacement: In recent years, smoke alarms powered by lithium batteries have been promoted in the hopes of reducing failures caused by dead batteries and by aging smoke alarms. These batteries are expected to last 10 years; after this time, the entire unit should be replaced.
- Use a qualified electrician to install hard-wired smoke alarms into the home's electrical system.
- Moving to a new location/residence: Smoke alarms should be replaced as the history/age of the alarms likely won’t be available.
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Manager, Research and Analysis, Alberta Emergency Management Agency |
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