CO Detectors

Came across this article this morning where a Home Inspector was consulted. Take a listen or read, I’m curious what your guys’ opinions are on him commenting and in regards to the information he provides. I’ll post my opinion later. Cheers.

On Your Side: Taking a closer look at Carbon Monoxide detectors |


CO is a little lighter than air so the alarm can go on the ceiling. The NFPA allows ceiling type alarms to be mounted there. The info in the video is incorrect.

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Yes CO is slightly lighter than air, however, it mixes with air so there is flexibility in where CO alarms can be placed. Always follow the manufacturer’s recommendation.

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Should the placement of carbon monoxide (CO) detectors be influenced by CO’s weight relative to air? - PubMed - NCBI
CO Detector Placement - Carbon Monoxide Kills

Not only is CO less dense than “air,” it’s typically introduced through a fuel-burning appliance/motor during operation. Therefore, the CO is heated and generally warmer than the areas where it is introduced, which means its tendency is to rise rather than fall.

Thanks for all your comments guys.

I kind of felt that there were two angles to this; one was that the information provided just wasn’t exactly correct and two was that the fella really went out on a limb getting recorded and quoted for broadcast even if he thought he really knew what he was talking about.

I think if you really dig in CO is lighter than “dry air”, a little bit of humidity (RH) changes things, but still at the end of the day the molecular weights are essentially the same and therefore CO does mix pretty well in air. That said he may have misspoke about CO being heavier than air, but if someone mounts a detector at the floor versus the ceiling they are probably not putting themselves at an elevated level of risk.

I like to mount them high to keep the pets and kids away from them and I also agree with Mr. Pope’s logic about CO being carried by warm air.

Regards all!