Chimney safety
Carbon monoxide detector placement, room by room
Do not light another fire until this has been looked at.
The short answer
One on every floor and outside every sleeping area. Everything else is detail.
Carbon monoxide detector placement comes down to coverage rather than height. CO mixes with air instead of rising or sinking, so the old advice about ceiling or floor level matters far less than having one on every storey including the basement, and one outside every sleeping area so it wakes you. What genuinely matters after that is what to avoid: within 15 feet of a fuel-burning appliance, in a bathroom, in dead air within a foot of a corner, and anywhere a draft or direct sun hits it. Those four cause the false alarms that get detectors unplugged.
No smell, no colour
There is no early symptom you can rely on. The detector is the entire warning system, which is why placement is not a detail.
Before we get there
What to do right now
None of this fixes it. All of it stops the problem getting more expensive between now and the visit.
If an alarm is sounding now: get everyone outside into fresh air, then call 911. Do not open windows first.
Press test on every detector you have. Test checks the horn, not the sensor, but a dead unit fails this too.
Look at the manufacture date on the back. Sensors expire at seven to ten years whatever the battery says.
Count your floors, including the basement. One detector per floor is the minimum, not the target.
Move any unit within 15 feet of a furnace, boiler or fireplace. That is the most common false-alarm cause.
What actually matters
Carbon monoxide detector placement, room by room
What to do, why it matters, and the part people most often get wrong.
One on every floor, basement included
Including levels with no appliance. CO travels through a house, and the floor where it is produced is often not the floor where somebody is asleep.
Outside every sleeping area
The whole point is that it wakes you. A detector two floors below a bedroom is protecting the hallway, not the person in it.
At least 15 feet from fuel-burning appliances
Close to a furnace or fireplace, normal start-up produces a brief spike that is not dangerous and will trip the alarm. Repeated false alarms are why detectors end up in a drawer.
Height is not the point
CO is close to the density of air and mixes with it, so it does not pool at the ceiling like smoke or at the floor like propane. Put it where you will hear it and where it will not be knocked.
Not in bathrooms, drafts or direct sun
Humidity, moving air and heat all shorten sensor life and cause spurious readings. Avoid within a foot of a corner too, where air is effectively still.
Replace the unit, not the battery, at 7-10 years
The electrochemical sensor degrades whether or not it has ever been triggered. A detector past its date can read zero in a room that is not.
Where to go next
Who handles this
The VIO Standard
- A written estimate first
- License and insurance checked
- Nothing starts without your OK
Good to know
Common questions
How many carbon monoxide detectors do I need?
Should carbon monoxide detectors be high or low on the wall?
Where should you not put a carbon monoxide detector?
Do carbon monoxide detectors expire?
Does a smoke alarm detect carbon monoxide?
The people behind every visit
Founded by Ryan Carter in 2019. Every page you read here is reviewed by Ethan Miller, our chimney specialist. A written estimate before any work, and the findings in writing whether or not anything needs doing.
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