I am looking at installing a carbon monoxide and natural gas detector on the ceiling of my house. I cannot find one device that combines both types of detection and that is supposed to be mounted in the ceiling.

Does anyone have any ideas about this? I would prefer to have one device, instead of two separate ones.


1 Answer 1


Here's at least one for you: http://firstalert.com/component/flexicontent/82-explosive-gas-co/929-plug-in-combination-explosive-gas-carbon-monoxide-alarm

I don't know why combination alarms are not more common. Maybe because natural gas has an odor added so it's readily apparent, unlike CO? There also aren't any dual smoke detector (ionizing and photoelectric) and CO combo alarms.

Note that CO alarms are usually mounted on the walls, not the ceiling, since CO is heavier than air and tends to sink a little [not true, as @Ecnerwal points out below]. I don't know if it's a big deal to mount it on the ceiling or not. I also don't know anything about optimal placement of methane detectors.

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    CO (12+16) is not heavier than air - 80% N2 (14+14) and 20% O2 (16+16) - it's "slightly less dense than air" as Wikipedia or high school chemistry will tell you.
    – Ecnerwal
    Jul 6, 2014 at 21:55
  • @Ecnerwal: You're right about the atomic weight, I don't really know why people say CO is heavier than air but I've definitely heard that. A quick check online seems to indicate that the placement of CO alarms doesn't really matter.
    – Hank
    Jul 7, 2014 at 0:56
  • Propane is more dense than air, so propane detectors must be near the floor or lowest point of the living space. Natural gas is lighter than air, so detectors for it should be on the ceiling.
    – wallyk
    Jul 7, 2014 at 3:43
  • For what it's worth, some the combined detectors I've seen offer the option of plugging the whole thing directly into an outlet, or snapping out the power supply, stretching out the cord, and mounting the detector some distance from the outlet. Convenient.
    – keshlam
    Sep 6, 2014 at 21:16

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