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Data Centers Breathe Easier With Less Oxygen
PC World is reporting that some companies are looking at a new method of fire protection in their server closets, oxygen-deprivation systems.""Wood stops burning when the oxygen content falls to 17 percent and plastic cables between 16 to 17 percent, said Frank Eickhorn, product manager for fire detection at Wagner Alarm and Security Systems GmbH in Hanover, Germany. Wagner makes electric compressors that use a special membrane to remove some of the oxygen from the outside air, a system the company calls OxyReduct. The excess oxygen is exhausted, and the remaining nitrogen-rich air is pumped inside the data center."
...er, so to speak. But it can't hold a candle to the burning excitement of watching pasty-faced geeks burn out, run out of steam, and pass out in a low-oxygen environment.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Hehe, I can just picture Simon locking someone in one of these and slowly dialing down the oxygen until he gets that raise or perk or whatever he's after.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
Yes, its safe to enter, but how long, 1 hour, 3 hours 6 hours 8 hours. The article doesn't mention.
Food not Bombs is a nice platitude but it breaks down when you notice that the Bombees are usually well fed
TFA is way too complex. There are much simpler ways to handle the problem. The oxygen levels in many major cities are below 18% already. Just let CO2 levels keep going up, this will push oxygen percentages down a tad more, and we have no more computer fires.
Space suits would be an immediate answer
If creativity is the field, copyright is the fence.
Now mountain climbing, hang gliding, and other low oxygen sports will be important on my resume!!
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Just imagine the new employee first day: ...
- Here is your cube
- Here is your chair
- Here is your scuba gear
It doesn't bind to the oxygen so much as just displace it. Halon is heavier than oxygen and just pushes it out of the area. Halon is dangerous though because if there are people in the room when it goes off they won't be able to breath.
This whole idea doesn't seem that great. So what if something shorts out and sits there glowing red and no one notices? You sure as hell notice when something starts burning but something could be slowing frying multiple components before anyone notices because there would be no signs.
Fire needs oxygen. More on this one as it comes in.
SSH?
Badass Resumes
Although I'm sure this is safe for day-to-day operations (for low-altitude data centers) and will prevent a self-sustaining blaze, I'd bet that a smoldering powersupply would convert an unpleasant fraction of the low-oxygen atmosphere into carbon monoxide. Oxygen-staved combustion tends to produce this deadly gas (which kills by binding to hemoglobin better than does oxygen)
Two wrongs don't make a right, but three lefts do.
The lower oxigen content just means that fires will not selfsustain. But if you have an external source for energy input, like the short you mentioned, thngs will still get hot and start to smoke. The chances are just a bit better that it does not cause a full-on fire.
You are not supposed to be working all the time in the serverroom anyway, it's much too noisy in there and your 200Watt of heat production would be much better used to warm your office.
In other words: you would have noticed that fire too late anyway if you had to rely on the amount of smoke coming from it.
This space is intentionally staring blankly at you
Proof by very large bribes. QED.
Its not exactly the same as being at 6000ft, its just similar from the perspective of how easily a human can breath. Higher altitudes have the same percentage of oxygen in the air, they just have lower air pressure, meaning less of all of its components. The lower altitude air will still be higher pressure, but with less oxygen. In terms of breathing, we just care about the partial pressure of oxygen, but thats not all that matters when it comes to whether something will burn.
Oh, say does that Star-Spangled Banner entwine / The myrtle of Venus with Bacchus's vine?
Just your memory doesn't function as well, so you better make all the passwords really simple.
Engineering is the art of compromise.
But it can't hold a candle to the burning excitement of watching pasty-faced geeks burn out, run out of steam, and pass out in a low-oxygen environment.
Watch an out-o'-shape pasty-tubby try to ride a bicycle some time: with all his belabored breathing, one would think he was climbing Everest instead of pedaling on level ground.
I, of course, am in perfect shape, with nary an ounce of extraneous tissue to be seen...
*looks around furtively*
*runs away*
*collapses after 30 yards*
I want to drag this out as long as possible. Bring me my protractor.
Been to 6000 feet and cooked many meals there on a camp stove. At 11,000 feet as well. Fire burns at that altitude just fine.
We had a similar issue when with the proliferation of large power-stations: water was pumped into cooling towers and then dumped in rivers. The cooling process de-oxygenated the water and this obviously meant the 'poisoning' of rivers (fish unable to breathe etc). We have a similar situation here. Only this time, the facility actually holds on to the oxygen. Why not mix it with the exhaust air (I'm sure it's not completely recirculated?) and avoid the potential for a similar situation. I know TFA says it's beathable, but it's worth considering the option nonetheless. Not all animals are humans. Remember what scale datacentres operate on, and which direection they're going in (they're not getting smaller). Has the potential not to be a significant issue...
-1 not first post
Not only are server rooms windowless, freakishly cold, and with uncomfortable chairs, but now they asphyxiate you too.
Boss (on telephone to sysadmin in data centre): "I'm sorry Dave, but your recent conduct just hasn't been acceptable. I've decided to invoke the disciplinary procedure, and having discussed this with Mr. Flibble we've decided that this warrants 2 hours of W.O.O."
Sysadmin: "What's W.O.O.?"
Boss: "With
"Slashdot - News and Chat Sites Deviant". (Click "homepage" link above for details).
That's because your fuel doesn't need higher concentrations of oxygen to ignite. With other materials that is not necessarily the case.
Still, I've been out of breath plenty in datacenters after pulling long lengths of (heavy) SCSI cables. I can't imagine trying to do that in an O2 Poor environment.
I read the internet for the articles.
Redesignate the open floor space as the management conference room. The oxygen will be sucked out in no time.
We don't do immersion because it doesn't work over the long term. In the short term, it's fine. Even in a closed system, though, degradation of components leads to the contamination of the coolant, which then must be cleaned.
Cleaning is itself a problem. All filters wear out, and no filters are perfect. The closest things you get are distillation, or reverse osmosis filtering. Distillation requires heat, and to clean that much water, too much heat will be needed. Reverse osmosis filters waste water, so the system won't be closed. In short, full immersion cooling is just a bitch.
Liquid cooling is fairly reasonable, but it has its own problems as well. If you have a centralized pump and centralized cooling for the coolant, then a leak anywhere is a leak in the entire system. If you don't, then you have a jillion pumps and radiators and all kinds of other crap to fail.
So liquid cooling is to be avoided in general, and full-immersion cooling simply isn't feasible.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
No, we exhale about 19% oxygen normaly. The bigger problem with rebreathing your own air is the buildup of CO2. That's why the astronauts on Apollo 13 were more worried about their scrubbers than their oxygen supply.
That which is done from love exists beyond good and evil
> Third; how much would a brain damaged BOFH cost you?
Dunno, are you assuming a brain damaged beyond the capability to enact revenge (which is pretty low-level wiring in the BOFH brain), or not ?
Great, now I have to wear a wireless bluetooth headset AND an oxygen mask when I'm on a tech support in the Data Center.
The guys in HR already call me "space man."
Partial pressure of oxygen determines combustability.
Amount of oxygen determines breathability.... which is how you can breathe astonishingly low pressures of pure oxygen in a space capsule.... till it catches on fire and makes a tasty dish of seared astronaut....
Gentoo Sucks
I saw this comment and saw that someone else had already explained this to someone else that had asked the same stupid question. But since you were modded up to +5 I guess I'll deal with this instance. The air in the data center at sea level with 14% oxygen has approximately the same amount of oxygen per cubic foot as the rarefied air at ~6,000 feet. Why? Because the air is denser. Note that TFA never claims that it is the same percentage of oxygen, only the same amount. These words mean entirely different things.
If you are a native english speaker, shame on you! You have no command whatsoever of your native language.
If you are not a native english speaker, I highly suggest that you return to your studies, because this language is stupid and you need more help with it. Don't feel bad - it happens to people of all countries who are trying to speak it. Including those who grew up speaking it.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
This might be safe for humans, but is it optimal for normal functioning. With a lower oxygen content, won't your lungs need to labor more to recover oxygen, and/or wouldn't your work ability be impaired somewhat (sleepiness etc) but the oxygen-poor air? This would be especially true if physical labour was required, for example lifting heavy servers on/off racks.
No, at 6000 feet there is still the same percentage of oxygen in the air, but at a lower pressure. This removes oxygen from the air. For a same volume of space it would have as much oxygen as a similar volume at 6000 feet.
Something will burn with the lower concentration of oxygen, but would be much less likely to ignite into open flame. It'd smolder slowly, and give you much more time to react to it.
It's a confusing analogy to explain a simple technical concept, because tech writers assume everybody is beneath their intelligence. Like putting too much air in a balloon.
I don't need no instructions to know how to rock!!!!
AFAIK, the percentage of oxygen is no different at altitude than at sea level, it is just the pressure of atmosphere is lower. So if I had to wager a guess, I would say that combustion is dependant on concentration of O2 per mass, and respiration is dependant on concentration of O2 per volume, which is why a smaller percentage of O2 has a greater effect on combustion then on respiration.
I think he may have been on the whacky-weed. The drill was always the same--everybody out, last one out the door hits the big red button for the Halon. It was just by the door and was protected under a plastic shield so you couldn't just bump into it by accident. Of course those were data centers constructed as the Earth was still cooling and before the dinosaurs became extinct. We were also entrusted with (or encumbered by) massive tape reels--one per drone--and expected to keep them safe until everybody could assemble and regroup. Just grand carrying one of those down five flights of steps from a computer room that was unaccountably located on the top floor of a building.
"Here's what's happening. You're starting to drive like your Dad..." - Red Green
A few decades ago I served on a submarine. The oxygen generator stopped working for a while, and for operational reasons we couldn't snorkel for fresh air. The percentage of oxygen dropped below the point where combustion is supported, so the smokers were out of luck. People's lungs respond to the partial pressure of oxygen in air, not the absolute percentage, so the crew including myself were fine, since we were only at about the equivalent of 10,000 feet (US units). I always wondered wouldn't it be safer from a fire prevention standpoint to always operate like that.
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.
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. 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.
Except that ppO2 = amount of oxygen (i.e. a ppO2 of 3psi is the same amount of O2 whether there's also a ppN2 of 12psi - roughly the composition of air at sea level - or it's pure O2). What you're thinking is that relative oxygen content determines combustability.
...following the principles of Heisenburger's Uncertain Cat...
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.
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.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
I worked in a USAF sim that had halon under the floors, but no chilled air flow under the floors, and the floor tiles had no vents. One day the fire alarm tech accidentally triggered the halon, and the air pressure under the floor tiles lifted the tiles up and off of their frames. And it blew all the under floor dust up into the room. I think it was $10K to replace the two tanks (1988). The programmer in the room at the time said it sounds more like a bomb than a hiss.
This incident occurred the day after we had a power supply convert itself into a "smoke generator", around midnight at shift change. It filled the sim with smoke. We ran in from the maintenance shop (through the sim was the way out too) the boss pulled the halon dump handle, and nothing happened. That's "Oh Shit" night, followed by a "Oh Shit" day. I think the fire alarm guys had a "Holy Fucking Shit" week.
- High Tech workers, please say NO to Union Carpenters, their Union sees fit to control our compensation.
It think it's the ratio of nitrogen to oxygen that matters, not the pressure.
The government can't save you.
At 6,000 feet or wherever, the oxygen concentration is still ~20%, albeit at lower pressure. This new product doesn't reduce the air pressure, it reduces the oxygen concentration. The effect on a human is approximately equivalent to being at 6,000 feet, but not exactly. In any event, it'll be a minor difference to you but a major difference to a fire.
Think of it in reverse: you can breathe oxygen at 100% concentration and not feel a whole lot different, whereas wood and plastic burn like gunpowder at that concentration.
FATMOUSE + YOU = FATMOUSE
Dave: Open the data centre door Hal
Hal: I'm afraid I can't do that Dave.
And your data center will float, too!
In a place I worked the computer room had a halon system. One day at shift change one of the operators caught a backpack strap on the mushroom button (even under the plastic mollyguard).. tore the button right off.
His first mistake was trying to put the button back.... whooosh!
halon stinks hours later.
Imagine your glowing red hot but not quite burning cable inside a low oxygen cabinet. The equipment isn't working well, some some poor tech is sent to fix it. Said tech opens the cabinet, introducing a lovely fresh mix of 21% oxygen into the cabinet, at which point the superheated pyrolized gasses mix with the oxidizer and you get what we in the fire department like to call...FLASHOVER....it's very bad for the complexion.
The problem with quotes on the internet, is that nobody bothers to check their veracity. -- Abraham Lincoln
People depend on the partial pressure of oxygen, fires the percentage. Thus on US submarines we let the sailors breathe down the oxygen to about 19% before turning on the oxygen generator to keep it at this level. Generating oxygen for people by water electroysis is energy intensive and requires about 500W per person. Now back to fires. As other smart readers of /. have pointed out fires burn at high altitude. In this case the percentage of oxygen is the same (20.9%) as at sea level but the partial pressure of oxygen is reduced which affects people to some degree depending on the person and work load. For the system described in the article one would need to use caution if it was used at high altitudes to make sure that people were not in an environment too low in oxygen.
In the "good old days" most sailors on submarines smoked and could tell when the oxygen level was down because they couldn't light or smoke their cigarettes.
Another aside: the Apollo moon capsule was maintained at about 3 psi of pure oxygen in space. They used lower pressure so the walls of the lunar lander could be very thin, I believe about 0.02 inches thick. The astronauts worried about accidently kicking a hole in the wall. This way the partial pressure of oxygen was the same as on the ground. The original design had the system on the ground at 100% oxygen for simplicity, with of course tragic results...it was modified to begin with normal air then change to 100% oxygen at lower pressure after launch. It was assumed that fires wouldn't burn in space because there is no convection due to zero g. This is flawed because fans are used to circulate the air. Fire in an environment where you are trapped is always a great concern.
We'd better buy 2, so we have a backup robot to repair the main one if it breaks down.
Better buy 3, in case number 2 goes down when repairing number 1.Halon 1211 (Bromochlorodifluoromethane) and Halon 1301 (Bromotrifluoromethane) have been banned in most countries since 1994 (The Montreal Protocol, as stated by the AC below) because they were found to deplete ozone.
As has already been stated, Halon worked as a fire suppressant by displacing oxygen, thus disrupting the fire triangle (fuel, oxygen, heat). Also, in the presence of any remaining flame or smoldering debris, Halon oxidized into other toxic gasses including phosgene which is very, very bad stuff and was used as a chemical weapon during WWI.
Like Carbon Tetrachloride extinguishers before them, Halon extinguishers had too many bad attributes; what we in the fire service would call, "Ethyl-Methyl-Bad-Shit".
In the US, OSHA safety standards require supplemental oxygen if the oxygen percentage drops below 17.5%. Defying this standard risks a worker lawsuit and some very nasty regulatory fines. Testing with gas monitoring equipment will be required to prove the oxygen level if it is ordinarily below the requirement. At some point, some one must do some work on the equipment. A human at rest may be able to survive quite well at lower oxygen levels but a person doing work may need to consume a higher amount.
Inergen is an inert gas fire suppression system that does exactly the same thing with a much smaller environmental footprint. The gas is generated with similar equipment, and then stored in bottles (similar to Halon et. al.) and then when a fire is detected, the room is flooded with said gas. The installed system is also much less expensive than the equipment.
See http://en.wikipedia.org/wiki/Inergen
From TFA:
They are not talking about oxygen free rooms. Yes, as your article says, breathing pure nitrogen will kill you as humans don't run on nitrogen. But that does not mean a high nitrogen content would be dangerous. Otherwise you would die as soon as you breathed a breath of Earth's air which is, by a long measure, mostly nitrogen. So your article really has nothing to do with this subject. Its sort of like giving a story of how 900 degree temperatures inside a cremation furnace affect the human body and using that as an argument on why people shouldn't be allowed in houses with the heat turned on.
Mathematics is made of 50 percent formulas, 50 percent proofs, and 50 percent imagination.
Saying your "phone ran out of batteries" is like saying your "car ran out of gas tanks".
Also, it is significantly better to have as much oxygen as possible while preventing fire -- flooding the center with pure nitrogen would be deadly unless you stopped while there was still enough O2 to breathe. According to the warning signs on the doors of the labs where I work, two breaths of pure nitrogen will knock you unconscious without any warning at all. Death will follow quickly...
*sigh*
I *realize* they aren't talking about O2 free rooms. Perhaps I should have picked a better article closer to nitrogen asphyxiation then one advocating it's use for the death penalty. My bad.
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. That's it- zip, nada- I'm all for fire-safing server rooms (GO HALON!). No motive to discredit this technology- and no interest IN discrediting it. Just simple information that your average person might not have known about...
And you'll get into trouble with the N2/O2 becomes about 95%- there's not enough O2 partial pressure (Depending on your lung capacity and general health) without the addition of helium- that N2 has to dissolve somewhere, too...
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.). 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.
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.
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. 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.
Note to ACs: I usually delete AC replies without reading them. If you want to talk to me, log in.
So if a fire starts, then it's like a balloon, and then something bad happens?
"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. 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.
Mathematics is made of 50 percent formulas, 50 percent proofs, and 50 percent imagination.
Since we're talking about how much oxygen is in a room I think I should point out that the standard atmosphere is around 21% oxygen and 78% nitrogen and 1% other.
Who is this Jimmy character, and why was he cracking corn in the first place?
Three breaths, huh? He must be a really slow breather. I could hold my breath for longer than it would take any normal person to take three breaths, with absolutely no danger of passing out, much less dying. N2 is inert. It is not poison. The worst it will do is displace oxygen, giving about the same effect as holding your breath. Since your brain can survive for I believe about 7 minutes without oxygen (although anything over what, 2 minutes I think, tends to cause some brain damage), you'd have to remain in a very low oxygen or oxygen free environment for that long before you'd have really serious problems.
SIGSEGV caught, terminating
wait... not that kind of sig.
Both you and the parent post are right, in a way.
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). 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.
In fact it is even worse than that, at 100 kPa oxygen (~one atmosphere of pure oxygen) flesh burns "vigorously", as my buddy's professor in combustion used to say. That's why you are not allowed any sort of lighter or match in a hyperbaric chamber, as people inside would burn as gasoline.
Victims of 9/11: <3000. Traffic in the US: >30,000/y
Not really. It takes about 20 seconds for blood from the lungs to reach the brain. If the blood is desaturated, you'll pretty much pass out instantly when this happens.
N2 is inert. It is not poison. The worst it will do is displace oxygen, giving about the same effect as holding your breath.
No. No. No. It's absofrigginlutely not the same. If you hold your breath, the blood can still take up oxygen from the air in your lungs, and the partial pressure of oxygen in the air in your lungs drops very slowly.
If, on the other hand, the gas in your lungs contains no oxygen (i.e. the partial pressure of oxygen is zero), then the blood will actually release oxygen instead of taking it up while travelling through the lungs, effectively becoming desaturated.
Roughly twenty seconds after you start breathing a gas mixture without oxygen, desaturated blood will reach your brain and it's lights out. Period.
No, breathing center in the brain detects only high CO2 levels. There are secondary effects of low O2 level, but you won't have enough time to feel them. Besides, these effects are subconscious - you usually don't notice them.
t rogen-6-11-03.pdf :
To quote http://www.csb.gov/safety_publications/docs/SB-Ni
"Breathing an oxygen deficient atmosphere can have serious and immediate effects, including unconsciousness after only one or two breaths."