Combination smoke and CO alarm
Covers both fire and carbon monoxide detection in one unit — useful near attached garages and fuel-burning appliances.
Compare on AmazonCarbon Monoxide Alarm Placement Checklist
Put a CO alarm on every level of the home, near each sleeping area, and near an attached garage. Keep alarms roughly 15 feet from fuel-burning appliances. Unlike smoke, carbon monoxide mixes evenly with air, so — unlike smoke alarms — mounting height on the wall matters much less.
Where CO alarms need to go
- One on every level of the home, including the basement.
- Near each separate sleeping area, close enough to wake occupants.
- Near (but not directly beside) an attached garage door, on the living-space side.
- Roughly 15 feet from fuel-burning appliances such as a furnace, water heater, or gas range — close enough to detect a leak, far enough to avoid nuisance alarms from normal operation.
The height myth
Smoke rises with heat, which is why smoke alarms go on the ceiling. Carbon monoxide is nearly the same density as air and mixes throughout a room regardless of where it's produced, so CO alarms don't need ceiling placement the way smoke alarms do — tabletop height, wall-mounted, or plugged into an outlet all work, as long as the alarm isn't blocked by furniture or curtains.
Replacement schedule
Most carbon monoxide alarms are rated for somewhere between 5 and 7 years, depending on the manufacturer — check your specific model's documentation rather than assuming it matches the 10-year smoke alarm rule.
CO alarms to consider
These links go to an Amazon search so you can compare current options and prices.
10-year sealed battery smoke alarm
A sealed 10-year battery alarm removes the annual battery-swap chore for the life of the unit.
Compare on AmazonInterconnected wireless smoke alarm kit
When one alarm sounds, they all sound — useful in larger homes or homes with long hallways.
Compare on AmazonStandalone carbon monoxide alarm
A dedicated CO alarm for rooms near fuel-burning appliances or an attached garage.
Compare on AmazonFrequently asked questions
Does CO alarm height on the wall matter?
Much less than for smoke alarms — carbon monoxide mixes evenly with air, so tabletop, wall, or plug-in placement all work as long as the alarm isn't blocked.
Do I need one in every room?
No — the standard guidance is one per level and one near each sleeping area, not one per individual room.
What triggers a CO alarm besides an actual leak?
Placing a unit too close to a fuel-burning appliance (within a few feet) can occasionally cause nuisance alarms from normal, safe operation — the roughly 15-foot guidance helps avoid that.
Related on HomeRuleCheck: the smoke & CO safety overview, when smoke alarms expire (the 10-year rule), how to dispose of an old smoke detector, and the smoke alarm coverage & expiration checker.