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Carbon Monoxide detectors: mount high or mount low?
Posted on 4/6/25 at 1:08 pm
Posted on 4/6/25 at 1:08 pm
An alarm contractor that I met told me that he used to install carbon monoxide alarms on the ceilings, and that the law required it, but that the building safety codes now require them close to the floor because it is a heavy gas, and where it will most concentrate.
I looked up where to install on Google and it says on the ceiling because it rises if heated.
Anyone here familiar with code on this?
I looked up where to install on Google and it says on the ceiling because it rises if heated.
Anyone here familiar with code on this?
8
Posted on 4/6/25 at 2:12 pm to HubbaBubba
My understanding is CO is lighter than air and will mix and tend to rise. Ours are mounted high.
“Heavy gas” that’s concentrates on floor seems wrong.
“Heavy gas” that’s concentrates on floor seems wrong.
Posted on 4/6/25 at 2:19 pm to HubbaBubba
I mounted mine in my house up high per the instructions. All of the RV's that I have had have them mounted low close to the floor.
Posted on 4/6/25 at 2:26 pm to HubbaBubba
Mount them high, but my understanding is not on the ceiling.
Posted on 4/6/25 at 5:30 pm to HubbaBubba
Copy and paste
The 2021 International Residential Code (IRC) and NFPA 720 (now rolled into NFPA 72) recommend following manufacturer instructions, which usually support ceiling or high wall placement. There is no code in the U.S. that mandates carbon monoxide detectors be installed low to the ground.
So your contractor may be thinking of propane detectors, which do go low because propane is heavier than air. But for CO? High is fine.
The 2021 International Residential Code (IRC) and NFPA 720 (now rolled into NFPA 72) recommend following manufacturer instructions, which usually support ceiling or high wall placement. There is no code in the U.S. that mandates carbon monoxide detectors be installed low to the ground.
So your contractor may be thinking of propane detectors, which do go low because propane is heavier than air. But for CO? High is fine.
Posted on 4/6/25 at 8:07 pm to HubbaBubba
Giving it a little thought, a carbon atom has an atomic weight of 12.011 amus, Oxygen has an atomic weight of 15.999amus. CO would be 26.010 amus while O2 would be 31.998 amus. I would expect CO to rise, even more so if it is hot due to being a product of combustion.
CO detectors should be placed high,and propane gas detectors should be placed low.
CO detectors should be placed high,and propane gas detectors should be placed low.
Posted on 4/6/25 at 8:11 pm to LSUtigerME
quote:
Mount them high, but my understanding is not on the ceiling.
The ceiling is fine though walls may be better but only slightly. At least 5 feet off the ground is the recommendation. Follow the manufacturer's recommendations.
Posted on 4/6/25 at 10:13 pm to HubbaBubba
Carbon monoxide is slightly lighter than air, so a CO detector should be mounted on the ceiling.
Natural gas is much lighter than air so a CH4 detector should be mounted in the ceiling.
Butane/propane are much heavier than air so their detectors should be mounted down low on a wall.
Natural gas is much lighter than air so a CH4 detector should be mounted in the ceiling.
Butane/propane are much heavier than air so their detectors should be mounted down low on a wall.
This post was edited on 4/6/25 at 10:15 pm
Posted on 4/7/25 at 7:18 am to RetiredSaintsLsuFan
quote:
All of the RV's that I have had have them mounted low close to the floor.
But that would make sense, as the CO source (generator) is low to the ground, and you'd want to catch it before it reached a detectable level in the top bunks, right?
Posted on 4/7/25 at 1:52 pm to Spankum
Thanks, all! Helps a lot the feedback from everyone. 
Posted on 4/7/25 at 2:08 pm to HubbaBubba
The old saying is "Mount them high and let it fly".
Posted on 4/7/25 at 2:38 pm to HubbaBubba
CO is a lighter molecule than CO2 and CO2 mixes well in the air.
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