In article .com,
"Pete C." wrote:

Joseph Gwinn wrote:

In article .com,
"Pete C." wrote:

Joseph Gwinn wrote:

In article .com,
"Pete C." wrote:

[snip]

Liguid CO2 isn't cryogenic like Liquid nitrogen, so a CO2 cooled
chamber
will be a good deal less dangerous than an LN2 one.

Like most any inert gas, CO2 will displace air and can be an issue if
enough is released in a confined space. Since it will sit low it
tends
to be a greater risk to children and animals, which probably aren't
an
issue in a work environment.

As far as I know, there is no CO2 mixed into medical O2. I have a
couple
med O2 cylinders here, and an oxygen analyzer and I read 100% O2.

There is one exception - treating cases of carbon monoxide poisoning.
If
I recall, the mix is 5% CO2 and 95% O2. The CO2 displaces the CO, and
the almost pure oxygen keeps you alive while this happens. Reportedly
it is very stressful to breathe this stuff - you feel that you cannot
get enough air, and yet are perfectly OK.

Joe Gwinn

Well, there is clearly more than one exception since my med O2 cylinders
contain *gasp* 100% O2. Also all my medical literature related to
emergency O2 use refer to 100% O2.

They may use two bottles and a proportional mixing valve.

Joe Gwinn

No, they do not. The two bottles are both 100% O2, the regulator
connects to one cylinder and directly feeds the mask(s), supporting one
adjustable continuous flow mask and/or up to two demand valve masks. The
two cylinders are strictly for run time.

I've not read any medical literature referring to administration of less
than 100% O2. Indeed the only place I'm aware of where breathing gas
mixes regularly contain more than 21% O2 and less than 100% O2 is diving
where it's called Nitrox or Enriched Air Nitrox (EANx). No breathing gas
mix I have ever seen deliberately contains any CO2, the mixes that do
contain it only contain it due to containing some percentage of ambient
air.

I do recall reading such articles, but a trip to Google revealed only
hints, perhaps a residue of pre-internet medical approaches. The
standard of care for carbon monoxide poisoning is now the hyperbaric
chamber, at 3 atmospheres. Hyperbaric chambers were uncommon 20 years
ago, so it does fit together.

Joe Gwinn