How often should carbon-monoxide alarms be tested?

CPSC recommends testing carbon-monoxide alarms monthly and replacing batteries at least annually unless the alarm uses a sealed battery. Follow the model's instructions and end-of-life signal.

Where should smoke alarms be installed?

The U.S. Fire Administration recommends smoke alarms inside every bedroom, outside each sleeping area, and on every level of the home, including the basement. Follow local code and manufacturer placement instructions.

How old is too old for a smoke alarm?

CPSC says smoke alarms more than 10 years old should be replaced. Carbon-monoxide alarm life varies by model, so use the manufacture date, instructions, and end-of-life signal.

Home › Advice › Smoke and Carbon-Monoxide Alarm Checklist: Test, Place, Replace

Smoke and Carbon-Monoxide Alarm Checklist: Test, Place, Replace

By Mark Phaneuf · Updated August 20, 2026 · Editorial policy

An illustrated house cutaway showing alarms on multiple levels and near bedrooms — Editorial illustration created for Safe Home Experts.

An alarm is not “fine” because the light is on. A useful alarm plan answers four questions: Is it in the right place? Does it test? Is it within service life? Does everyone know what to do when it sounds?

If an alarm is sounding now

Treat a smoke or carbon-monoxide alarm as a real warning. Get everyone outside to fresh air and call 911 or the fire department from outside. Do not search the house for the source, silence the alarm and go back to sleep, or re-enter until responders say it is safe.

Carbon monoxide cannot be seen or smelled. Headache, dizziness, weakness, nausea, vomiting, chest pain, and confusion can be symptoms of exposure, but do not wait for symptoms before leaving.

The room-by-room placement check

For smoke alarms, the U.S. Fire Administration recommends units:

inside every bedroom;
outside each separate sleeping area;
on every level, including the basement.

CPSC recommends carbon-monoxide alarms on every level and outside sleeping areas. Local building and fire codes may require more. Garages, kitchens, fuel-burning equipment, high ceilings, and manufactured homes can create model-specific placement rules, so follow the alarm manufacturer's distance and mounting instructions.

Do not place an alarm based on a convenient screw hole. Steam, cooking aerosols, dead-air spaces, fans, vents, and fuel-burning appliances can affect placement.

The five-minute monthly test

Tell everyone you are testing.
Use the test button—do not use a flame, exhaust, or improvised smoke.
Confirm the sound is audible in sleeping areas.
Replace a weak battery or nonresponsive unit according to its instructions.
Record the date and any action taken.

CPSC recommends monthly carbon-monoxide alarm testing. Use the smoke-alarm schedule in the manufacturer's instructions; a recurring monthly household test keeps the routine simple.

Find the manufacture and replace-by dates

Remove the unit only as its instructions allow and find the manufacture date on the back or side.

Smoke alarms: CPSC says to replace units more than 10 years old.
Carbon-monoxide alarms: service life varies. Follow the manufacturer's replacement date and end-of-life signal.
Combination alarms: follow the model's shorter applicable replacement schedule.

Write the replace-by month on the unit or in your home record. A fresh battery does not extend an expired sensor's life.

Battery and power rules

Replace removable batteries on the schedule in the instructions; CPSC says at least annually for CO alarms.
Never remove a battery to stop nuisance alarms without fixing the cause and restoring protection.
A hardwired alarm may still have a backup battery and can still reach end of life.
Sealed 10-year batteries are not user-replaceable; replace the alarm when the battery or unit reaches end of life.

If interconnected alarms do not all sound during the prescribed test, use the manufacturer's troubleshooting steps or call a qualified electrician/alarm professional. Do not open hardwired electrical boxes unless you are qualified and authorized to do that work.

Make the response automatic

Add this to the household emergency sheet:

outside meeting place;
two ways out of each sleeping area where possible;
who helps children, older adults, visitors, or pets;
911 and local fire department contact;
alarm locations, model numbers, and replace-by dates.

Practice the exit. The alarm's job is to buy warning time; the household plan is what turns that warning into action.

Quick answers

How often should carbon-monoxide alarms be tested?: CPSC recommends testing carbon-monoxide alarms monthly and replacing batteries at least annually unless the alarm uses a sealed battery. Follow the model's instructions and end-of-life signal.
Where should smoke alarms be installed?: The U.S. Fire Administration recommends smoke alarms inside every bedroom, outside each sleeping area, and on every level of the home, including the basement. Follow local code and manufacturer placement instructions.
How old is too old for a smoke alarm?: CPSC says smoke alarms more than 10 years old should be replaced. Carbon-monoxide alarm life varies by model, so use the manufacture date, instructions, and end-of-life signal.

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Sources

CO Alarms — U.S. Consumer Product Safety Commission
Smoke Alarms — U.S. Fire Administration
Fire Safety Information Center — U.S. Consumer Product Safety Commission

Mark Phaneuf is the publisher of Safe Home Experts and president of Ikan Media Inc. He edits practical homeowner guides from primary sources and clearly separates safe homeowner checks from work that belongs with a qualified professional. He is not a contractor, engineer, insurer, or financial adviser.