CARBON MONOXIDE HAS NEARLY THE DENSITY OF AIR. CO is slightly lighter. You can figure this out. For example:
O=16 C=12 N=14 H=2
You would add things to get the pure density of gasses.
H2 = 1+1 = 2 (very light)
O2 = 16+16 = 32 (slightly heavy)
N2 = 14+14 = 28 (about neutral)
CO2 = 12+16+16 = 44 (heavy)
CO = 12+16 = 28 (about neutral)
H2O = 1+1+16 = 18 (light) - as in humidity or steam
Radon = 222 (very heavy)
So what is the density of air? The air we breathe is composed of 80% Nitrogen, 19% Oxygen, .6% inert gases and .4% Carbon Dioxide.
N2 + O2 + CO2 = ?
.8( 28 ) + .196(32) + .004(44) = 28.9 (by definition air is neutral)