On Sun, 2 Jul 2006 12:12:44 -0500, "Rick"
wrote:

Lets look at the safety of both suggestions.

1) Nitrogen liquid will boil to gas. The gas is an asphyxiate. Many people
have died from nitrogen. Air contains 21.5% O2 mostly the rest is N2. If
you breath pure N2 the first breath you pass out and the second breath brain
damage and the third death. Think about passing out when reaching for
something in the ice chest. If you fall in your dead; if you fall out you
will probably be ok. The next day you will be ripping out your N2 system.
A closed boat can accumulate N2 which will displace air. Maybe get you in
your sleep or when you go down for a cold one.

2) CO2 is heaver then air and would accumulate in the low parts of the boat.
Same issue as with N2 but it would at least give you some warning signs.

Whats wrong with a little water from melting ice. You are on a boat
right???


Nitrogen displaces oxygen, so you pass out without warning. It is not
otherwise toxic. So figure being underwater for a few seconds. That's
as much time as you have with N2. With CO2 you pant.
Both gases diffuse of course.

Brian Whatcott Altus OK

Brian Whatcott wrote:
Nitrogen displaces oxygen, so you pass out without warning. It is not
otherwise toxic. So figure being underwater for a few seconds. That's
as much time as you have with N2. With CO2 you pant.
Both gases diffuse of course.

"Carbon dioxide is a colourless gas which, when inhaled at high
concentrations produces a sour taste in the mouth and a stinging
sensation in the nose and throat. These effects result from the gas
dissolving in the mucous membranes and saliva, forming a weak solution
of carbonic acid."

Material Safety Data Sheet
Gaseous Nitrogen:

SIMPLE ASPHYXIANT
Section 3 : HAZARD IDENTIFICATION
Emergency Overview:
Nitrogen gas is colorless, odorless and non-flammable.

It is non-toxic. The primary health hazard is asphyxiation by
displacement of oxygen.
Route of entry:
Inhalation, skin and eye contact.
Effects of acute exposure
Eye contact:
Vapor may cause a stinging sensation.
Skin contact:
No adverse effects from gas.
Inhalation:
May cause dizziness.
Asphyxiant.
Can cause vomiting.
May result in unconsciousness.
May cause excitation, excess salivation, rapid breathing.
May cause headaches and drowsiness.
May cause stinging of the nose and throat.
Ingestion:
Not a likely route of exposure.
Effects of chronic exposu
None known. Chronic exposure to abnormal concentrations unlikely
Reproductive effects:
Oxygen deficiency during pregnancy has produced developmental
abnormalities in humans and experimental animals.

Brian Whatcott wrote:


Nitrogen displaces oxygen, so you pass out without warning.

Nitrogen does not *displace* oxygen (O2 weighs more than N2). Excess
Nitrogen will reduce the partial pressure of oxygen. Respiration is
controlled not only on CO2 concentration, but on blood pH and O2
saturation as well. N2 does not bind with hemoglobin, and does not
significantly affect blood pH. As a result, an excess of N2 will cause
further depletion of oxyhemoglobin in the red blood cells (less than 25%
is typically transferred, leaving a reserve factor which prevents your
sudden passing out scenario). This results in a higher respiratory rate
due to low O2 saturation, as well as causing a higher partial pressure
of CO2 (bicarbonate in solution), further lowering the pH of the blood,
and triggering the same reactions as does CO2. CO2 does it somewhat
more quickly is all.

It is not
otherwise toxic. So figure being underwater for a few seconds. That's
as much time as you have with N2.

I'm afraid I don't understand what this is trying to say.

With CO2 you pant.

As you will with N2. Increased CO2 will initiate higher respiratory
rates more quickly than decreased O2 saturation rates will, since the
homeostatic control sensors are more sensitive to CO2.

Both gases diffuse of course.

Which is why, with any reasonable implementation, neither N2 (although
the handling hazards of liquid N2 make it fairly useless IMO) nor CO2
are an issue.

Keith Hughes

Brian Whatcott wrote:
Nitrogen displaces oxygen, so you pass out without warning.

Keith Hughes wrote:
Nitrogen does not *displace* oxygen (O2 weighs more than N2). Excess
Nitrogen will reduce the partial pressure of oxygen.
Snip

Once again, this is copied directly from the MSDS (Emphasis added):

Material Safety Data Sheet
Gaseous Nitrogen:

SIMPLE ASPHYXIANT
Section 3 : HAZARD IDENTIFICATION
Emergency Overview:
Nitrogen gas is colorless, odorless and non-flammable.
It is non-toxic. The primary health hazard is asphyxiation by
displacement of oxygen.

Snip

Brian Whatcott wrote:
Nitrogen displaces oxygen, so you pass out without warning.


Material Safety Data Sheet
Gaseous Nitrogen:

SIMPLE ASPHYXIANT
Section 3 : HAZARD IDENTIFICATION
Emergency Overview:

Inhalation:
May cause dizziness.
Asphyxiant.
Can cause vomiting.
May result in unconsciousness.
May cause excitation, excess salivation, rapid breathing.
May cause headaches and drowsiness.
May cause stinging of the nose and throat.


So maybe lots of warning before passing out. But like others have said,
it only happens at extreme concentrations.

On Mon, 03 Jul 2006 20:20:36 -0400, Sailaway
wrote:

Brian Whatcott wrote:
Nitrogen displaces oxygen, so you pass out without warning.


Material Safety Data Sheet
Gaseous Nitrogen:

SIMPLE ASPHYXIANT
Section 3 : HAZARD IDENTIFICATION
Emergency Overview:

Inhalation:
May cause dizziness.
Asphyxiant.
Can cause vomiting.
May result in unconsciousness.
May cause excitation, excess salivation, rapid breathing.
May cause headaches and drowsiness.
May cause stinging of the nose and throat.


So maybe lots of warning before passing out. But like others have said,
it only happens at extreme concentrations.


Though your MSDS cites supported a point of mine previously, I try to
recall that MSDS are heavily contaminated with lawyer inputs.
I have seen the baro chamber tests that I find more convincing.

Brian Whatcott Altus OK

Brian Whatcott wrote:

snip

Though your MSDS cites supported a point of mine previously, I try to
recall that MSDS are heavily contaminated with lawyer inputs.
I have seen the baro chamber tests that I find more convincing.

Brian Whatcott Altus OK

I've been personally involved in some MSDS generation processes (needed
for cleaning validation of pharmaceutical processes), and I can tell you
from experience that lawyer inputs are probably one of the lesser
contaminants in the process. OSHA doesn't generate these things, the
folks making the chemicals do. Not suggesting anything nefarious, just
noting that some of these folks, IME, don't have all their dogs barking.

Keith Hughes

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...)


OK?

Brian Whatcott Altus OK

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

On Wed, 05 Jul 2006 09:19:03 -0700, Keith Hughes
wrote:

I'm trying to point out that it can be done, and done safely, as
long as reasonable care is taken.

And it *has* been done for many years by myself and others with no
problems whatsoever. The only real hazzard is touching the dry ice
with bare skin but that is easily avoided.