> >Weighing roughly 150 % as much as air, it sinks like a stone.  The hive has
> >to be sealed pretty completely for it to be a problem.  CO2 leaving
> >the cluster soon cools and drops, then runs out the entrance like water.
>
>    I'm not sure I accept the above. Granted that CO2 is heavier than
> O2 (it's also heavier than N2, which makes up 4/5 of the atmosphere in
> the first place), I sincerely doubt that it's molecular weight difference
> will be enough to offset normal diffusion throughout the hive's
> internal atmosphere.
 
Good points.
 
Well, if we're talking wintering here - and I think we are - the
amount of CO2 release is pretty slow and spread over time - into
still air; hence the stone analogy.  But maybe it is not a good
one.
 
> Remember, there are (hopefully ;-) tens of
> thousands of bodies in some motion in the hive, and "drafts" of
> molecules should allow the atmosphere to be fairly well mixed interally.
> This should make striation of atmospheric constituents insignificant,
> I would think.
 
Well, the bees are in a fairly tight, still cluster.  CO2 will be at
its highest concentration there, one would think .  If it rises
significantly, the cluster loosens.  Hopefully there will not be much
stirring air motion in the hive - merely a slow convection current up
and through - unless there is a strong wind outside.
 
And the CO2 released is not pure, but at a fairly low concentration.
 The air released from some part of the cluster will be warmer than
the surrounding air as in the original post, but also - heavier when
cooled a bit.  It also contains significant water vapor.  We know
from observation that it goes up and out the top entrance from the
steam that emerges.
 
If there is no top entrance, then we wonder where the water and the
CO2 goes.  Water vapor should be lighter than air, but it tends to
condense on cool surfaces in the hive.
 
So the question is whether the CO2 rises to the top as originally
proposed, intermixes with the air completely, or runs out the bottom.
 
I propose that all three may be true to some extent.
 
> Note that the above argument WOULD make sense in the case of gasoline
> fumes, but they are typically many hundreds (if not thousands) of
> times greater in weight than O2, or CO2, etc.
 
Well, not to get into gasoline, propane, etc., I think over the time
frame we are considering, several factors come in:
 
-one is the number of air changes that are able to take place.
-another is the amount of stirring action occuring
-another is the natural settling of a heavier substance,
-and yet another is the tendancy for solutions to form.
 
Even in the case of completely miscible substances - like the gases
in question, mechanical action or time is required for diffusion.
 
If sufficient air exchange occurs, the question is moot.
 
At any rate, I think we are agreed that CO2 will not accumulate
unuasually at the top of the hive with the cluster - even without an
upper entrance or other provision for upward air flow.
 
I suppose the question that remains is whether there will be any air
exchange through a bottom entrance due to heavier air leaving and new
air replacing it (convection).  I believe there will always be some
due to incomplete intermixing of air. This is unless the hive is
entirely and tightly sealed and there is only one small  hole at the
bottom.
 
It doesn't take much of a crack to supply enough air for a cluster.
 
However it becomes fairly apparent that without regular air changes
that CO2 and H2O will accumulate in the hive and may reach
problematic levels.
 
I think that it is equally apparent that too many air changes could
result in loss of heat and moisture to the detriment of the colony.
Regards
 
Allen
 
W. Allen Dick, Beekeeper                                         VE6CFK
RR#1, Swalwell, Alberta  Canada T0M 1Y0  Internet:[log in to unmask]
Honey. Bees, Art, & Futures <http://www.cuug.ab.ca:8001/~dicka>