Data centers breathe easier with less oxygen – slashdot anoxemia

I was *trying* to point out that you don’t want to get too carried away by ‘inerting’ areas because there are consequences- while you may become sleepy and tired from CO poisoning, or disoriented, hot, and suffocating from CO2 poisoning, people will not experience warning symptoms with N2 poisoning- they’ll simply keel over.

You will only get the simply keel over effect if oxygen levels are 0 (or close to it), like if you suck on a hose spouting pure nitrogen. The same thing will happen if you start breathing pure CO2. If you are in an environment where your body cannot get the oxygen it needs, you will simply die.


If on the other hand you get a more gradual fall in oxygen levels (which would be the most common failure scenario here, as well as in most everyday situations where CO2 levels rise), you will feel side effects first.Anoxemia and anyways, as long as you have reasonable safety precautions, its still not going to rise to the level of they’d better make damn sure NO ONE can defeat the safeties to get into that room, like you said in your first post. I mean if you are going to keep people out of any enclosure where there may be a drop in oxygen levels, you would also have to keep them out of houses and apartments that are heated with natural gas (which may result in a methane leak).

Just simple information that your average person might not have known about…

I’m pretty sure the average person knows you need oxygen to breathe.

Halons work to extinguish fire using several mechanisms. Oxygen displacement- not absorption or binding- is one of them, but if this were the only factor, then dry nitrogen, carbon dioxide, or other inert gas would work just as well.Anoxemia

There are four things required for combustion: oxidizer, fuel, heat, and a chemical reaction that is self-sustaining- the chain reaction, in which free radicals are formed. Halons work by kicking off chlorine, bromine, or fluorine radicals in the heat of the fire, ending these reactions. Unfortunately, the same properties that make this class of compounds so wonderful for extinguishing fires is also what makes them so good at terminating the production of ozone.

I also seem to recall something in my distant past as a fire instructor that halons as a group have a fairly high specific heat, meaning they carry away more heat from the fire; this is a relatively minor factor when compared to things like water which have high specific heat and very high heat of vaporization.Anoxemia water is surprisingly good at putting out electrical fires; energized systems can be handled by using distilled water, as was done at browns ferry nuclear power plant in tennessee in 1975. But it’s messy and doesn’t fight three dimensional fires very well.

Replacements such as FM-200 and novec 1230 that do not survive long enough to reach the stratosphere have been made and are now available. They are comparable in effectiveness to more traditional halons (halon 1211 and 1301), and novec is shipped as a liquid rather than a compressed gas. This makes it safer and less expensive to transport. Being fluorinated molecules (no chlorine, just fluorine) less phosgene is produced during a fire, which is a good thing.Anoxemia

It think it’s the ratio of nitrogen to oxygen that matters, not the pressure.

Nope, it’s the percentage of oxygen and the pressure. Multiplying pressure by percentage for each gas gives you the partial pressure of that gas, and it’s the gradient of partial pressures that determines rate of absorption. Well, to be precise, gas in your tissues (lung tissues, blood, etc.) has tension, not pressure, so it’s the difference between the partial pressure of the gas in what you breathe and the partial tension of the same gas in your tissues that determines absorption rate.

To live, you need a ppo2 within a certain range. IIRC, between about 0.05 (5% at 1 atm, or 10% at 0.5 atm, etc.) and 2.4 (pure O2 at 2.4 atm, or 50% at 4.8 atm, etc.).Anoxemia below that range, oxygen doesn’t diffuse into your tissues fast enough to supply their needs, above that range the oxygen begins to damage the tissues, in an effect known as oxygen toxicity.

SCUBA divers who go to great depths take bottles with very low percentages of oxygen, low enough that the gas would be marginal for survival at the surface. They do it because at, say, 20 atm (600 feet), normal air has a ppo2 of about 4.2, far, far above the safe level. A 3% O2 mix at 20 atm, however has a comfortable ppo2 of 0.6. Since the deep mixes aren’t breathable in shallow water, such divers either carry multiple bottles of different gas mixtures (don’t mix ’em up!) or else have pre-positioned staged for appropriate depths.Anoxemia

Going the other direction, pilots, astronauts and mountain climbers spend time in environments with very low pressures, low enough that the ppo2 is not survivable (or at least is not conducive to strenuous activity). So they breathe high concentrations of O2, usually from bottles of pure O2.

Cardiovascular efficiency also plays a major role here. Good cardiovascular health means both increased lung surface tissue for absorption and higher-volume blood flow for delivery of absorbed gases to the tissues which in turn absorb them from the blood (mostly according to the partial tension gradient with a tissue-specific absorption coefficient). So, people with good cardiovascular health can survive lower ppo2 levels.Anoxemia

Nitrogen has no effect on any of this, except as a gas to fill up the non-oxygen part of the mix, and, for divers a gas that will be absorbed under high pressures and released from tissues as pressures decrease. The bends is just nitrogen coming out of solution too fast and forming bubbles which block blood vessels.

CO2, on the other hand, is poisonous. I don’t recall what the levels are, but above a certain ppco2, you pass out and then die. CO2 must be removed from your breathing gas. This isn’t an issue for open circuit SCUBA divers, whose exhalations float off to the surface, but it’s important for rebreather divers and, obviously, for astronauts and others in sealed environments.

Bringing this back to the topic at hand, 17% O2 shouldn’t be a problem for anyone of normal cardiovascular health unless the data center is located on a high mountain peak.Anoxemia someone who has some lung injury or deficient circulation wouldn’t want to work in such a data center, but most such people routinely use a nasal flow of pure O2 anyway so, again, it shouldn’t be a problem.

It’s the difference between the partial pressure of the gas in what you breathe and the partial tension of the same gas in your tissues that determines absorption rate.

Nitrogen does nothing, but it is in the way. Oxygen has to diffuse through nitrogen to get to a place where it is consumed, and diffusion is a relatively slow process (yes, I am a chemical engineer, and I did run stefan-maxwell simulations).

Say you have a total pressure of 20 kpa, 100% oxygen. If oxygen is consumed at point X by a reaction (I will drop the issue of products diffusing out), all other oxygen around will rush to the spot unhindered (pressure is fast: actually the limit would be the speed of sound).Anoxemia if you have dry air atmosphere, you have 20 kpa oxygen and 80 kpa nitrogen. If oxygen is consumed at point X, nitrogen will accumulate there since air as a whole, not oxygen only, are dragged to point X, and only oxygen is disappearing.

So, yes, what counts for reaction rate is the partial pressure of oxygen, but in many cases (and fires are one of these) diffusion limits how fast oxygen can get to the reaction, so you cannot just pretend you do not have an inert gas in the way.

People cook out up in estes park at 9-13K all the time. Maybe dude needs to refill his lighter…

It isn’t just the partial pressure of oxygen that’s important for fire. It’s also the partial pressure of nitrogen. Nitrogen cools the reaction without contributing to it.Anoxemia

So having the partial pressure of oxygen appropriate to 6,000 feet while having even greater than sea-level partial pressure of nitrogen could well keep a fire from burning (at least in some fuels) and make it much harder than usual to get one started even in things (like magnesium) that would be happy to burn in this atmosphere (or even in pure nitrogen).

Meanwhile the human body is mostly interested in the partial pressure of oxygen and carbon dioxide. Walking into the data center would be like suddenly going from local altitude to 6,000 feet (minus the ear-pops and potential for a case of pressure-related issues). You’d run a little less brightly than usual. Live in such conditions 24/7 for a month or so and you’ll build up additional hemoglobin in your blood until (like people who live at altitude) you’re just fine. (I don’t know if you’ll get back to full power living in them 8/5, though.)