Caution: Smoke Detector Alarms Have A Shelf Life

Last updated on November 16th, 2018


Smoke detectors expire. Over time they lose sensitivity. The last thing you want is a weak smoke detector in your room while sleeping soundly at night.

Here’s what you need to know…

The smoke detector ‘works’ largely unnoticed while on the ceiling or walls while it constantly and continuously measures the air around it – just waiting to alarm.

It works hours, days, weeks, months, years – never ending.

At least until one of two things happen…

1. The batteries run dead.
2. It’s shelf life expires.

Note: A good habit to get into for replacing smoke detector batteries is during every New Year. January 1 seems like as good a day as any…

But did you know that smoke detectors lose their effectiveness over time?

The U.S. Fire Administration says most smoke detectors installed today have a life span of about 8-10 years. After this time, the entire unit should be replaced.

It is a good idea to write the date of purchase with a marker on the inside of your smoke detector’s (battery compartment) so you will know when to replace it. Some of the newer detectors already have the purchase date written inside.

Someone asked why there’s a 10 year shelf life when the shelf life of an ionization smoke detector’s “Americium 241” has a half life of over 400 years. Good question.

I suspect that the NFPA recommendation may have to do with electronic components aging and/or the reliability thereof. Electrolytic capacitors ‘dry out’ for example. Also, a dual sensor smoke alarm additionally includes a photoelectric sensor which may be affected over time.

“It is the sensors that fail after a given amount of time, not so much the electronic circuitry or the radioactive ionization source. The sensor modules rely on an electro-chemical reaction to smoke/CO, they get saturated over time depending on exposure and also just plain start breaking down.”


About Smoke Detectors (Important!)

There are many different brands of smoke alarms available on the market but they fall under two basic types: ionization and photoelectric.

Ionization alarms sound more quickly when a flaming, fast moving fire occurs.

Photoelectric alarms are quicker at sensing smoldering, smoky fires.

Dual Sensor alarms combine ionization and photoelectric into one unit.

Because both ionization and photoelectric smoke alarms are better at detecting distinctly different yet potentially fatal fires, and because homeowners cannot predict what type of fire might start in a home, you might consider installation of both ionization and photoelectric or dual sensor smoke alarms.

The Best Dual Sensor Smoke Alarm:

The following smoke alarms are what I have installed in my own home. I have several of the AC (hardwired) units and I’ve also added a few battery powered smoke alarms in other locations.

Battery Powered

AC Powered (hardwired) with battery backup

More: Dual Sensor Smoke and Fire Alarm, and Why They Are The Best

Fire Escape Plans
You should have escape plans and make sure everyone in the household knows them.

Fire Extinguishers
Have several fire extinguishers!
Consider one in the bedroom and one near the kitchen (at least!).

How To Put Out A Grease Fire.

You should also install a Carbon Monoxide Detector!
Carbon monoxide is winter’s silent killer.



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