Greetings and welcome aboard the CF, Ufoysterman.
Originally Posted by akkebeng
CO (carbon monoxide) is actually a fraction lighter than air but not as much to prevent it from rapidly mixing with the air ...
Originally Posted by Cowboy Sailer
Carbon monoxide is not heavier than air. It is slightly lighter than air. It diffuses very well in air.
I see that two of us posted almost at the same time.
Since the molecular weights of gases differ, what makes them move is convection. If a gas is released because of combustion, it would tend to rise due to its heat. CO is very slightly lighter than air*.
It is very unpredictable where the air, and therefore CO, will move at any given time. That is why the instructions with the unit you buy do not say to place it high or low on the wall.
Understanding all that, the National Fire Protection Association (NFPA) suggests in 720, 2-1.1.2* 1998 -
"A carbon monoxide alarm
or detector should be centrally located outside of each separated sleeping area in the immediate vicinity of the bedrooms. Where bedrooms are separated and the audibility of the alarm
or detector to occupants within the bedroom area could be seriously impaired, more than one unit could be needed. Each alarm or detector should be located on the wall, ceiling, or other location as specified in the installation
instructions that accompany the unit."
I recommend installing CO detectors at about face height, when sleeping.
Air has a molecular weight of 29
Carbon monoxide (CO) has a molecular weight of 28.01
Carbon dioxide (CO2) has a molecular weight of 44.01