New Fine Woodworking magazin almost made me ill

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Doug Miller wrote:

I suppose this is strictly true. There is nothing wrong with nitrogen.
My point is a nitrogen-only atmosphere will cause death in humans, and the humans will have no advanced notice of the danger.
Hence the (perhaps wrong) potential danger of Halon fire suppression systems that use nitrogen.
Again, I welcome more and better information. I know I often get things wrong.
-- Mark\
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Mark, I think the difference is that here we are talking about nitrogen as a propellant, which would dilute the oxygen content somewhat. In the NASA case, nitrogen was used in large quantities to displace the air. To put it in silly terms, spaying water on the fire will raise the humidity of the room, but not hurt the human occupants. Flooding the room with water to remove all of the air will result in drowning.
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alexy wrote:

I agree I have probably fixated on an obscure and basically irrelevant point. ;-) That's my MO. <g>
Doubtless halon was/is an effective fire suppressor.
Sorry for the diversion... ;-) I specialize in obscure and irrelevant....
-- Mark
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You are *not* 'entirely wrong' in that premise.
As with everything else, everything depends on the details. :)
The 'typical' Nitrogen-pressurized HALON system uses HALON 1211, a sprayable liquid. The gas pressure is used to force the liquid out of the storage tank, through the pipes, and out into the 'protected' space.
It _is_ practical to install cut-off valves that pass the liquid flow, but shut themselves off when the gas starts going by. Doing so, however, _does_ add a fair amount of complexity, and _cost_, to the system.
You get into a _very_ complex set of trade-offs, regarding the size of the protected space, the layout, the number of people in it, how _quickly_ they can evacuate, given a warning, and the dollar cost of letting the fire burn 'without resistance' for that evacuation period.
One of the other HALON formulations (I don't have the number to hand) is built around a bromine atom. "Bromides" are _not_ 'people friendly'; this is the kind of a system where you absolutely *have* to evacuate before the dump goes.
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Long ago when I was in the air force (about 1955) and on flying status we were required to go through high altitude training. In a pressure chamber we were brought to an altitude of 40,000ft. then every other man in the chamber unplugged from his oxygen then started to write his name on a clip board after what seemed like a couple of seconds his partner plugged him back in. In just a couple of signings the writing from neat to an unreadable scrawl. Then a volunteer was selected (military remember) told to stand with his arms out like an airplane, he was unplugged and given commands to bank right, bank left, climb, dive. After the bank left command he just stood in that position until he was plugged back in to the oxygen. I always thought what an easy way to go no pain no strain your just gone. It was also one lesson that stayed with me every time I flew.
Bob P. making sawdust in Salem Or.
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Theres an old B&W Hollywood movie featuring the U.S.A.F. that has a _very_ realistic scene in it of that pressure chamber testing. It's not 'Fail Safe'; not 12 O'Clock High setting _is_ in the United States; I don't think it's 'Strategic Air Command'; It _might_ be in the one (who's name escapes me) about training 'bombardiers', and how they deserve equal 'credit' with the pilots.
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"IIRC"? That is a big IF!
You are partially right. If increase the normal air nitrogen content from 78% to 90% or 95%, there is precious little room for oxygen. But I suspect you would experience shortness of breath.
Maybe you were thinking of carbon monoxide?

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alexy wrote:

Pi approximately = 3.14159 26535 89793 23846 26433 83279 40288 41971 ... I have verifiable memories from 1960 before I was a year old. My memory is either a gift or a curse. Since I'm *not* *rich* it must be a curse ... ;-) It's a hell of a burden to recall 45 years of accumlated failures in 3D, TechnicalColor detail....
BTW I *SUCK* at most things. In scientific terms I have "narrow bandwidths of more-than-minimum competence." Einstein said that everyone was somehow his superior; I know that almost everyone is in nearly every way better at everything than I am. (<sigh> Ask my wife and kids....)
F*ck.
-- Mark
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I'm told a job as a sex toy pays really well. <guffaw type=muffled degreedly>
Sorry, couldn't resist.
When you leave the door _that_ wide open, *somebody* is going to drive the truck through it. I guess I'm "somebody" around here, today. :)
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The insidious thing is that you _don't_ experience shortness of breath. The CO2 is also driven out, and the breathing reflex doesn't cut in. You _don't_know_ you're in breathing trouble, because you've "forgotten" to breathe.
The 'hypoxia' suffered at high altitudes (mountain climbers, flyers) is _exactly_ the same thing.
It's similar to 'nitrogen narcosis' for SCUBA divers,
All of these things just 'sneak up on you' -- you don't know there's anything wrong.
With _mild_ hypoxia, *IF* you've had training to recognize the symptoms _in_yourself_, you *may*: (a) recognize that "you're *IN*TROUBLE*", (b) manage to remember 'what to do about it', (c) actually _do_ it.
Severe hypoxia can hit fast enough, and hard enough, that you _don't_ have any chance. You're unconscious before you're conscious (pun intended) that there's a problem.
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"Not exactly". <grin>
Nitrogen, itself, is absolutely harmless. Good thing, too, because it makes up approximately 80% of what you're breathing _right_now_. It is an *inert* gas, totally non-reactive with _anything_.
That said, a 'near-total' nitrogen atmosphere *is* dangerous. Not so much _because_ of the Nitrogen presence, but because the levels of (a) Oxygen and (b) Carbon-Dioxide, are at unsafely _low_ levels -- 'driven out' by the excess Nitrogen.
Nitrogen is 'colorless, odorless, and tasteless' (good thing!, see above:), and, as such, you get no warning of the presence of a 'too nitrogen rich' environment.
The absence of CO2 means that the 'breathing reflex' is _not_ triggered, and you simply 'forget' to breathe. This _lack_ of CO2 is the 'real' killer -- you "don't know" you have a breathing problem, because you aren't "feeling the need, the need to breathe". Fairly quickly, this leads to oxygen depletion in the blood stream, which leads to cessation of many 'automatic' bodily functions. Unconsciousness follows. 3-5 minutes later, and you have irreversible brain-death due to lack of oxygen.
Catch the unconscious person promptly, remove them from the 'unhealthy' environment, and they will generally recover quite quickly. "Mouth-to-mouth" is actually the most effective 'direct' treatment -- it supplies the critical carbon-dioxide as well as the oxygen. Speed _is_ of the essence in getting breathing restored. Ephinepherine may also be beneficial -- it assists hemoglobin in binding to free oxygen.
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snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) wrote:

Robert, I am not a medical professional, and Jr. high school biology was a long time ago, so I might be wrong, but aren't you ascribing to atmospheric CO2 what is really an issue with dissolved CO2 in the blood, or possibly CO2 build-up in the lungs? After all, this mechanism works when you are holding breath underwater, with no CO2 in the surrounding "atmosphere". Excessive CO2 buildup in the lungs is removed by breathing air with or without normal atmospheric levels of CO2.
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wrote:

That is correct: the level of CO2 in the atmosphere is very, very low, approximately 0.035%, or only 350 ppm. The breathing reflex is triggered by the level of CO2 in lung tissue.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter by sending email to autoresponder at filterinfo-at-milmac-dot-com You must use your REAL email address to get a response.
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Yes.
Er, no. Plenty of nitrates, nitrites, and other nitrogen-containing compounds exist. It's not one of the noble (inert) gasses, those are the helium/neon/argon/krypton/xenon/radon column.

Yes, but that CO2 is in blood-chemistry, and is a result of cellular respiration rather than CO2 in the atmosphere.

I've been an EMT for a dozen years, and have never heard this theory. Can you provide a link I can read about it please? We provide 100% oxygen in situations like this, by bag/valve/mask in most cases. Mouth to mouth is only used until/unless we can get high-flow O2 on them, because exhaled breath has considerably _less_ than the 21% O2 that's in the atmosphere. It's certainly better than nothing, but nowhere near as good as pure O2. The breathing drive isn't needed at that time, because we're pushing it into them if they're not breathing well on their own.

At the EMT level of training, we use epi to raise blood pressure by constricting the blood vessels, and improve ventilation by opening up the air passages in the lungs. I am surprised to see that it has an effect on oxygenation of hemoglobin.
Dave Hinz
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Dave Hinz wrote:

snip
years ago. http://www.scuba-doc.com/latenthypoxia.html Joe
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Cmon Robert, that is what his point was! Read it again.
Robert Bonomi wrote:

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Always got to be some SOB wants to argue. Today, it's me. There are several inert gasses. Helium, Neon, Argon, Radon... Nitrogen is fairly non reactive but everything from ammonium nitrate fertilizer to nitric acid tends to show that is does react with a few things. Doesn't require extreme conditions, either. Check out the rhizobium bacteria attached to the roots of your alfalfa or clover.
bob g.
every thing else you said appears to be right on.

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Get in line ;)
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On Thu, 18 Nov 2004 15:36:00 +0000, snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) wrote:

We were able to "drop in" - more or less - FM1200. It used the same distribution pipes but required a larger canister.
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"FM 200" maybe? I can't find any apparently relevant on-line references to "FM1200"
FM 200 _is_ one of the closer substitutes, and the 'most commercially available'. It fails the 'drop-in' replacement test on at least a couple of points -- 1) tanks have to be kept in a controlled environment, HALON is ok, outside in the Arctic, or the tropics. 2) can't use it through long piping runs.
All the 'gory details', for anybody who is interested, at: <http://p2library.nfesc.navy.mil/P2_Opportunity_Handbook/3_III_2.html
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