That's true for CO2, but CO is actually slightly less dense than air (1.20 kg/m^3 vs 1.23 kg/m^3 according to Wikipedia), and tends to mix with air or rise slig

That's true for CO2, but CO is actually slightly less dense than air (1.20 kg/m^3 vs 1.23 kg/m^3 according to Wikipedia), and tends to mix with air or rise slightly above it: http://www.ehow.com/way_5545497_proper-elevation-carbon-monoxide-detector.html http://www.ehow.com/way_5545497_proper-elevation-carbon-mono...