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Does pushing the test button on a smoke alarm test the smoke sensor device inside?
Friday, June 29, 2018
Using the test button on the smoke alarms around your home regularly to verify that they are functional is recommended by alarm manufacturers. The test button checks two parts of the system: it verifies that the alarm is receiving adequate electrical power to function and that it will go off if activated by the smoke sensor.
But the test button does not test the sensor to verify that it will properly respond to smoke in the air and activate the alarm. There are aerosol cans of non-combustion “smoke” that cost around $10 and are approved to actually test the sensor inside the alarm. But most people aren’t going to go to all that trouble and will simply push the test button once in a while—which is, by the way, all that most manufacturers recommend doing.
There is a second safety precaution, however, that manufacturers recommend, and that is replacing the alarm when it is 10 years old. Ten years is the rated lifespan of the sensor. By that time it will have been operating continuously for 87,600 hours, and also accumulated a layer of dust on the internal components. So, whether the sensor is still functional is iffy at best.
Most smoke alarm manufacturers mark the date of manufacture or the date of the 10-year anniversary for alarm replacement on the back of the alarm. We check alarms that aren’t obviously new for manufacture date during a home inspection, and call them out for replacement if they are older. The back of the Firex smoke alarm in the photo at the top of this page, for example, has a stamp indicating it was manufactured on March 1, 2005, and is therefore past the end of its rated 10-year lifespan.
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