The 60-Second Carbon Monoxide Check Most Homes Skip

Your detector has a test button. Here is what it does and doesn’t prove.

Pressing the test button on a carbon monoxide detector proves one thing: the alarm and the battery work. It does not prove the sensor can still smell gas. Sensors age, and most manufacturers put a replace-by date on the back of the unit for that reason.

What to check

Turn the unit over and find the manufacture date. Most electrochemical sensors are rated for five to seven years, and a surprising number of homes are running detectors well past that. If there is no date, assume it is old.

Where it should be

Carbon monoxide mixes evenly with air, so height matters less than location. One detector on each level, one outside every sleeping area, and nothing within a few feet of a fuel-burning appliance where normal startup could trip it.

The habit

Test monthly, replace batteries twice a year when the clocks change, replace the unit at the date on the back. The whole routine takes a minute and it is the one household check that has no do-over.