I am going to do an engineering guess and say that the density of CO2 gas at
room temperature is 0.11 #/ft. So for 300 ft/min it works out to 33# per
minute. Now that's a lot of dry ice subliming but something less then 5400
# per minute.


"Keith Hughes" wrote in message
...

Brian Whatcott wrote:
On Mon, 03 Jul 2006 16:55:28 -0700, Keith Hughes
wrote:


Brian Whatcott wrote:



Nitrogen displaces oxygen, so you pass out without warning.

Nitrogen does not *displace* oxygen (O2 weighs more than N2).

//

Keith Hughes


This sort of technical thread too easily turns into a ****ing contest,
I realise.
So when I say nitrogen displaces oxygen, do tell me what happens when
I introduce a nitrogen generator of 300 cu ft /min into a closed room
of 1000 cu ft.
The nitrogen displaces the room atmosphere does it not?
(Whether the prior atmosphere in question is all oxygen, all hydrogen,
all helium, all whatever...)

No, it does not. In a "closed room", you would merely be pressurizing the
room, and reducing the partial pressures of whatever gases were there to
begin with. If the room is vented, then it would depend on the relative
densities of the N2 and the original gases, and the configuration of the
inlet and the exhaust vents. I do these types of studies all the time in
cleanrooms, autoclaves, EtO chambers, and purging and overlaying
containers with N2, and they are not simple processes.

And let's put your scenario in the context of the discussion, 300 ft3/min
of CO2 would require sublimation of 5400 lbs/minute.



OK?

My point was that, unlike say, propane, adding Nitrogen to air gradually
dilutes the O2 content. It doesn't displace it like a heavier gas would,
where, rather suddenly, you'd be submerged in a blanket layer. The result
is a gradual diminution of O2 that the body will detect, and respond to.
The response is increased respiration, which will work until the O2 gets
below about 10%.

And unlike your generator scenario, where you simply pressurize a vessel,
or flush a vessel designed for purging, the "generator" in real life is
very, very small, and boats are not sealed.

I'm not trying to win a ****ing contest, but let's remember that the
response to the OP was, to paraphrase 'do it and you'll die', which was
singularly unhelpful, and inaccurate relative to the question of using
reasonable quantities of dry ice in a cooler, in a typically vented boat.
I'm trying to point out that it can be done, and done safely, as long as
reasonable care is taken.

Keith Hughes