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

Hmmm....brainfart. 1 Lb of dry ice sublimes to 250L of CO2 gas, or
about 8.8 ft^3. So, 300 ft^3/min would requie about 34 Lbs/minute.
That's still a lot of dry ice :-)

Keith Hughes

Rick wrote:
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

There in lays the futility of this debate. A 24x18X18 cooler with a typical
R value of 7 and an internal temperature of 0F in an 80F cabin will gain
about 190 BTUs per hour which will melt about 3/4 pound of dry ice to form
about 6 cu.ft of CO2.

Unless you are sleeping on the floor right next to the cooler in a sealed up
cabin there is not a lot of danger.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Keith Hughes" wrote in message
...
Hmmm....brainfart. 1 Lb of dry ice sublimes to 250L of CO2 gas, or about
8.8 ft^3. So, 300 ft^3/min would requie about 34 Lbs/minute. That's still
a lot of dry ice :-)

Keith Hughes

Rick wrote:
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