DTaylor said; "
An LP gas detector should be mounted as low as possible since LP gas is heavier than air. (sinks to lower levels)
A carbon MONOXIDE detector should be mounted at ceiling level since it is lighter than air, therefore rising to the upper levels.
Smoke detector should be mounted at ceiling level since the products of combustion are lighter than air.
http://www.engineeringtoolbox.com/specific-gravities-gases-d_334.html "
And thanks for that. I have never heard of a combination CO and LP detector! Because of the different weights of these gases/fumes detectors must be at different heights!!
Would appreciate a reference if anyone believes that a combo. will work.
John