Home Safety

How Often to Test Smoke & Carbon-Monoxide Detectors

Detectors are the cheapest life-safety devices in your home and the easiest to forget. Testing takes thirty seconds a month — and the replacement date matters more than most people realize.

The short answer

• Test every alarm once a month by holding the test button.
• Replace removable batteries at least once a year — sealed 10-year units never need one.
• Replace smoke alarms 10 years after the manufacture date, no exceptions.
• Replace CO alarms every 5 to 10 years, depending on the model — check the label.

How to test one properly

1. 1Warn anyone home — it's loud, and it will startle pets.
2. 2Press and hold the test button until the alarm sounds, usually 3 to 5 seconds.
3. 3Listen for a full-volume horn. Weak or muffled means replace it.
4. 4On interconnected alarms, confirm the others sound too — that's the whole point of the wiring.
5. 5Vacuum the vents with a brush attachment while you're there; dust causes false alarms.

What the chirps and beeps mean

• Three loud beeps, repeating: smoke. Get out, then call.
• Four loud beeps, repeating: carbon monoxide. Get everyone outside into fresh air, then call 911 or the gas utility.
• A single chirp every 30 to 60 seconds: low battery.
• Chirping that continues after a fresh battery: end of life — the unit is telling you to replace it.

Where they need to be

• Smoke alarms inside every bedroom, outside each sleeping area, and on every level including the basement.
• Keep smoke alarms at least 10 feet from the stove to cut down on cooking false alarms.
• CO alarms on every level and outside each sleeping area — plus near an attached garage.
• CO mixes evenly with air, so height is flexible; follow the manufacturer's instructions.

The expiry date almost everyone misses

Sensors degrade whether or not the alarm has ever gone off. Take one down and look at the back: there's a manufacture date printed on it. If it's more than 10 years old — or past the replacement date on a CO unit, which is often 7 — it belongs in the recycling, not on the ceiling. An expired detector gives you the reassurance of protection without the protection.

Where CO actually comes from

Carbon monoxide is odorless and comes from anything that burns fuel: the furnace, water heater, gas range, fireplace, or a car warming up in an attached garage. Most incidents trace back to a cracked heat exchanger or a blocked flue — which is the real argument for an annual furnace service alongside working alarms.

Turn it into a habit you don't have to remember

A monthly test and a yearly battery are trivial tasks with an outsized payoff — they just rely entirely on memory. Add your detectors to Upkeepery and it schedules the monthly test, the battery change, and the 10-year replacement date, then reminds you when each one is due.