[TheForge] vent hood

Mon Jan 5 18:17:29 2004

C=12 amu (atomic mass units)
N=14 amu
O=16 amu
hence CO = 28 amu and CO2=44 amu
whereas O2=32 amu and N2=28 and air (80% N2) averages about 29 amu.

Therefore if you put room temp. CO in a weightless balloon, the balloon
will neither rise nor fall, whereas if you put room temperature CO2 in
such a mythical balloon, it will fall.

However, exhaust gases from a furnace are nowhere near RT.  Their
densities will diminish in proportion to their absolute temperature.  To
make a long story short, they'll go up.  By the time they've cooled
enough to come back down, they'll be thoroughly mixed with the
surrounding air.  And you can't separate gases on the basis if density
because they diffusively mix too rapidly.

BTW, I have previously posted cautions about propane being dangerous
because it's heavier than air.  Propane is C3H8, MW=44, same as CO2. 
However, propane will come out of the bottle at or below RT, so is very
likely NOT to mix well with the air, but to drop to the floor and
collect in sumps.  It will not be pure propane collecting in these
places, but an air-propane mixture, which just might be in the flammable
range.  Hence the danger.

Bruce
NJ

>>> [email protected] 1/3/2004 12:42:57 AM >>>

I have to wonder if it would actually be better to vent close to the
floor 
seeing that CO and CO2 are heavier than air.... I think so anyway.

                Ted Jones

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