Smoke and CO alarm maintenance: schedule, lifespan and costs
Updated
Overview
The smoke and carbon monoxide alarms are the cheapest things in the house and the ones that matter most. A smoke alarm wakes you before a fire blocks the way out. A carbon monoxide alarm warns of a gas you can't smell, from a furnace, a water heater, a fireplace, a generator or a car in the garage. Both are simple devices with a sensor that ages and a battery that dies, and their maintenance is a test every month, batteries every year, and replacement by the date on the back. The fire extinguishers are on the list below because they're the other half of the same job.
Lifespan
Smoke and CO alarms last 5 to 10 years. A smoke alarm's sensor is good for 10 years from its manufacture date, whether or not it's ever gone off. A carbon monoxide alarm's sensor is a chemical cell that's used up over 5 to 10 years, depending on the model. Neither failure shows on the test button, which checks the horn and the circuit but not the sensor, which is why the date on the back is what decides replacement.
What shortens an alarm's life is dust, cooking grease and insects in the sensing chamber, and a location in a humid or hot spot. What extends it to its full term is keeping it clean with a vacuum now and then and keeping it where the maker says. The signs an alarm is near the end: a date on the back close to or past its limit, a housing that's yellowed, false alarms that come more often, and an end-of-life chirp that a new battery doesn't stop.
Maintenance schedule
The test, the batteries, the replacement and the extinguishers, in the order they come due.
| Task | How often |
|---|---|
| Test the smoke and CO alarms | once a month |
| Replace the smoke and CO alarm batteries | once a year, or twice if you tie it to the clock change |
| Replace the smoke and CO alarms | every 10 years for smoke alarms, every 5 to 10 years for CO alarms |
| Check the fire extinguishers | a quick check once a month |
Replacement cost
A new alarm costs $15 to $60. A basic battery smoke alarm is at the low end, and a combination smoke and carbon monoxide alarm with a sealed 10 year battery, or a hardwired interconnected unit, is at the high end. A house needs an alarm in every bedroom, outside each sleeping area and on every level, so replacing the whole set runs to several alarms.
The repair-or-replace rule: there's no repair. An alarm that fails its test with a fresh battery, chirps with a new battery, or is past its date is replaced. The only decision is which kind: a sealed-battery alarm trades the yearly battery change for a full replacement at 10 years, and a hardwired alarm with a battery backup is what most homes built in the last few decades have and should keep.
Common problems
- An alarm chirps every minute: a low battery. Replace the smoke and CO alarm batteries, and if the chirp continues, the alarm is at its end of life.
- No sound on the test button: a dead battery, a failed alarm, or on a hardwired unit, a tripped breaker. Test the smoke and CO alarms again after the battery, then replace the unit.
- Frequent false alarms: a dirty sensing chamber, steam or cooking smoke, or a sensor that's unstable with age. Vacuum the alarm, and if the false alarms continue, replace the smoke and CO alarms.
- Every alarm in the house goes off at once with no smoke: interconnected alarms following one faulty unit. Find the one with the blinking light and replace it.
- A carbon monoxide alarm sounds and nobody feels ill: it may still be a real reading. Leave the house, call the gas company or the fire department, and don't go back until it's cleared.
- A fire extinguisher's gauge has left the green: it's lost pressure. Check the fire extinguishers monthly and replace one that's out of the green or past its date.
FAQ
How long do smoke alarms last?
About 10 years from the manufacture date on the back. Carbon monoxide alarms last 5 to 10 years. The test button doesn't measure the sensor, so the date is what counts.
How much does a smoke alarm cost?
$15 to $60, from a basic battery alarm to a combination smoke and CO alarm with a sealed battery.
How often should smoke alarms be tested?
Once a month, by pressing the test button on each one until it sounds.
Where should smoke and CO alarms be placed?
A smoke alarm in every bedroom, in the hallway outside each sleeping area, and on every level including the basement. A CO alarm near the sleeping areas and on every level with a fuel-burning appliance or an attached garage.
Why does my smoke alarm keep going off for no reason?
Dust or insects in the chamber, steam from a nearby bathroom, cooking smoke, or an aging sensor. Clean it, move it if it's too close to the kitchen or bathroom, and replace it if it's past its date.