Well let me give you my method and introduce a little controversy. I am new to coal but not new to chemistry. this is my issue. As pointed out in this thread many people for whatever reason are relying on CO detectors that are not giving them the safety they wish for. A little background:
Carbon monoxide has nearly the same density as air.
You'll notice that the manufacturer's instructions that come with the
detector don't say high or low either.The density of a gas is proportional to the weight of a single molecule of
that gas.So you figure relative buoyancy for yourself if you start learning a few
H=1, He=4, C=12, N=14, O=16.
Add them up for the molecular weights of pure gasses:
H2 = (1+1) = 2, very light
He = (4) = 4, very light
N2 = (14+14 ) = 28, about neutral
O2 = (16+16) = 32, slightly heavy
CO2= (12+16+16)= 44, heavy
CO = (12+16) = 28, about neutral
CH4= (12+4*1) = 18, light (majority part of natural gas)
H2O= (2*1+16) = 18, light (steam)
C2H6=(2*12+6*1)= 30, about neutral (minority part of natural gas)
C3H8=(8 + 3*12)= 42, heavy (propane)
C4H10=(10+4*12)= 58, (butane)
C5H12=(12+5*12)= 70, pentane, lightest part of gasoline
For mixed gasses just take a proportionate average:
Air is 80% N2 + 20% O2 .
air = 0.8(28) + 0.2(32) = 29 (exactly neutral, by definition)
So pure carbon monoxide is actually about 3% lighter than air.
But usually it is made in modest concentrations, mixed in with the normal
combustion products: CO2, H2O. Which are always mixed with the 80% Nitrogen that never participates in
burning. Then that mixes with room air, making an even smaller concentration...
And there are uncertainties...
Some fuels make light exhaust (more H2O), some make heavy (more CO2).
Then when the exhaust cools the light part, H20 (steam), may condense and
drop out. Not to mention that the exhaust gas was expanded when hot, and it
contracts as it cools.
No rule can predict which way it is going to go in most circumstances.
There is however, one constant in all of this and that is CO is a product of incomplete combustion. It can climb up stairs or descend to the basement. The issue is it is heterogeneous in most homes and the detector near the furnace may or may not give you the right reading or any reading at all even if it is working correctly. I have helped develop some industrial units and my feeling is I don't trust them. Ensuring an overabundance of make up air is the best way to safety and I don't even have one in my home.
There that should stir tings up.
Regards to all