CO Detector- Go High or Go Low?

At almost every home inspection I do there is a conversation about carbon monoxide (CO) detector(s) and where they should be placed in a home for proper protection and monitoring for elevated CO levels.

It seems there is a common belief that CO is heavier than air so the detectors should be placed close to the floor. The reality is that carbon monoxide is actually slightly lighter than air and tends to diffuse evenly throughout a room. However, since CO is usually a byproduct of combustion gasses that enters the home through warm air, there is a greater chance of higher CO levels up high in a room.

So where did the idea of putting the monitors close to the floor come from? Pure practicality in my opinion… since many standalone CO detectors are the plug-in type they end up close to the floor because that’s where the outlets are. In a perfect world, the CO detectors would be placed about 5 feet from the floor, but it’s rare to see that.

Both plug-in type CO detectors and ceiling mounted CO or combination smoke/ CO detectors will provide adequate monitoring for elevated levels of CO. What’s more important is that they are installed, and that at a minimum there is one detector on every floor of the home that has rooms used for sleeping, and within 15 feet of each of those rooms. Also, most CO detectors have a lifespan of 5 years and should be replaced if they are any older than that.

More info on on CO detectors provided by the City of Portland can be found here.