Smoke Detector Replacement
NFPA urges replacing home smoke alarms after 10 years
Quincy, MA, October 23, 2001—Replacing batteries in home smoke alarms will be a
common ritual this weekend for many people as daylight savings time ends. But if
smoke alarms in your home are more than 10 years old, NFPA (National Fire
Protection Association) recommends replacing them, as well.
Why? According to 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% probability of failure within the first 10 years. Newer smoke alarms
do better, but should be replaced after 10 years. Unless you know that the smoke
alarms are new, replacing them when moving into a new residence is also
recommended by NFPA.
Smoke alarms, when properly installed, give an early audible warning needed to
safely escape from fire. That's critical because 85% of all fire deaths occur in
the home, and the majority occur at night when most people are sleeping. Last
year, NFPA documented 3,420 home fire deaths.
Fully 94% of U.S. homes had at least one smoke alarm as of 1997, according to
NFPA, but as of 1998, 40% of the home fires reported to U.S. fire departments
and 52% of home fire deaths still occurred in the small share of homes with no
smoke alarms. Half of the deaths from fires in homes equipped with smoke alarms
resulted from fires in which the smoke alarm did not sound--usually when
batteries were dead, disconnected or missing.
"Simple steps like maintaining smoke alarms and replacing older ones help
diminish the possibility of fire deaths in the home," says John R. Hall, Jr.,
NFPA's assistant vice president for fire analysis and research. "Smoke alarms in
the home are largely responsible for the decreasing number of home fire deaths
over the last decades."
How soon should you replace your alarm? This is a value judgment. Only 3% of
alarms are likely to fail in the first year, and annual replacement would be
very expensive, so that doesn't make sense. At 15 years, the chances are better
than 50/50 that your alarm has failed, and that seems too big a risk to take.
Manufacturers' warranties for the early alarms typically ran out in 3-5 years.
So, in ten years there is roughly a 30% probability of failure before
replacement. This seemed to balance safety and cost in a way that made sense to
the responsible technical committees.
If a 30% 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 home smoke alarms, when they fail, tend to fail totally, as opposed to
hard-to-detect creeping failure, such as a loss of sensitivity.1 Regular monthly
testing will help discover alarm failure as well as a dead or missing battery.
You can replace your alarm when it needs replacing.
The same study showed all the inoperable alarms tested in 1992 were at least 5
years old and predated a 1987 change in product standards that reduced
sensitivity to reduce nuisance alarms. Changes in alarm chip design, among other
improvements, make it likely that electronic failure now occurs at a rate much
less than 4 times per million hours of operation.
Replacing alarms after 10 years protects against the accumulated chance of
failure, but monthly testing is still your first, best means of making sure
alarms work. Today's alarms are even less vulnerable than the original alarms.
Regular maintenance of the more sophisticated systems used in larger buildings
can keep them working very reliably for many decades.