Carbon Monoxide Alarms

Bonneville70

What is the best position to mount a CO2 alarm? Carbon monoxide is heavier than air therefore should an alarm be fitted low down in a motorhome as opposed to high up?  I have fitted mine about a foot up from the floor so that the wife and I don't die in
the night should there be a problem. During my time in British Army of the Rhine a number of soldiers died through sleeping on the ground near a carbon monoxide source. That tells me an alarm should be fitted low down and not high up. Thoughts on this would
be welcome.