Fire and breathing in nitrogen-rich air

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In summary, living at high elevations with lower oxygen levels, such as 4000 m above sea level, can cause mountain sickness and require days for adaptation. However, airplanes are pressurized to a level of 160 mbar oxygen, causing a rapid drop in pressure and potential problems due to pressure changes. Oxygen also plays a crucial role in fire prevention, with lower levels of oxygen making it difficult for fires to start and spread. This has led to the development of Oxygen Reduction Systems, which use nitrogen to lower the oxygen levels in a building and prevent fires. This method has been supported by studies showing that low oxygen levels can explain high extinction rates in the past. However, some species, such as bar-headed geese and certain
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snorkack
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People routinely live above 4000 m, where oxygen partial pressure is under 130 mbar. True, we often suffer mountain sickness there, and take days adapting to the height as we walk up.
But airplanes are only pressurized to 760 mbar total, 160 mbar oxygen. And that drop, from 210 mbar to 160 mbar, happens in a few minutes as the plane climbs, with the few problems being caused by pressure changes, not lack of oxygen.

Now, note that while oxygen undergoes exothermic reactions to burn, very few substances (like Mg and Li) are capable to fix nitrogen.

Nitrogen takes up heat. Therefore in an environment where oxygen concentration is lower than 21 %, even though oxidation reactions like breathing still happen and release heat, the heat is spread to larger amount of nitrogen molecules, the peak temperature reached is lower, and that temperature most reactions are slower - and this hampers thermal runaways like fire.
Many common flammable substances cease to burn at surprisingly high oxygen concentration - like wood already at 17 %.

So...
Would it be safe to fill a room with gas of 12...13% oxygen, the rest nitrogen?
To prevent accidental suffocation on pure nitrogen of 0 % oxygen, it would make sense if the nitrogen is already mixed with 12...13% oxygen while stored.

True, 12...13% oxygen entered into rapidly (under a minute) might cause a mild impairment. But breathing fire and smoke also causes rapid impairment of a man.

Also, if air is stored in metal pressurized bottles, at room temperature and around 200 bar pressure, and suddenly released in case of need, it cools by Joule-Thompson effect. IIRC by about 30 degrees. So, cold air flow at about -10 Celsius can also be mildly impairing to man, but not seriously so. Would a blast of cold air at -10 Celsius and 12 % nitrogen be effective in blowing away fires and cooling overheated objects?
Now, 12...13 % oxygen is mildly impairing to man.

Would 15...17 % oxygen be a comfortable and safe environment to work in permanently, to avoid fire breaking out in the first place?
 
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Perhaps see..

http://www.n2firefighter.com/pagina.php?lingua=en&cod=1

N2 FIREFIGHTER®: fire prevention with Oxygen Reduction System
O.R.S (Oxygen Reduction System)
The N2 FIREFIGHTER® methodology prevents the development or spreading of open fires by adding nitrogen to the atmosphere.

Until recently, the focus was to discover a fire as quickly as possible and to extinguish it effectively. Technological progress, careful and meticulous studies during these decades made it possible to greatly reduce the risk of fires in general. However, a new method, based on the depletion of Oxygen, has opened completely new venues for us.

We are now able to create fully protected environments and to completely eliminate the fire hazard by changing the atmosphere within a building by allowing full access to people at the same time.
 
  • #4
from: https://www.livescience.com/6981-gasping-air-lack-oxygen-worsened-great-dying.html

Raymond Huey and Peter Ward of the University of Washington have shown that a reduced supply of oxygen could explain high extinction rates that preceded the Great Dying, as well as the very slow recovery that followed.

Currently, oxygen makes up about 21 percent of our atmosphere, but in the early Permian period it was 30 percent. From this invigorating level, it fell to about 16 percent at the time of the Great Dying and over the next 10 million years continued to drop to 12 percent.

Paper: http://science.sciencemag.org/content/308/5720/398

Oxygen levels in the late Permian went to as low as 12%, which caused existing species to be restricted to low elevations with higher air pressure, for example. So, derive what you want but you are using mostly long extinct species as examples, not mammals or birds (dinosaurs).

Also consider Barheaded geese flying over the Himalayas:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4346704/

Note the extreme conditions and actual changes in metabolism required. FWIW: early dinosaurs were well-adapted to lower oxygen (like many modern migratory birds) and became important at the close of the Permian.

And lastly - there are human populations that are adapted to much lower oxygen levels (due to elevation), see the physiology and anatomical changes here:
https://www.ncbi.nlm.nih.gov/pubmed/9881522
 
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1. How does fire behave in nitrogen-rich air?

Fire requires oxygen to sustain itself, so in nitrogen-rich air, the fire will not have enough oxygen to continue burning. However, nitrogen gas itself is not flammable and can act as a blanket, suffocating the fire.

2. Is it safe to breathe in nitrogen-rich air?

No, it is not safe to breathe in nitrogen-rich air. Our bodies require oxygen to function, and nitrogen gas does not provide us with the necessary oxygen. Breathing in pure nitrogen gas can lead to suffocation and even death.

3. What are the effects of breathing in nitrogen-rich air on the human body?

Breathing in nitrogen-rich air can result in hypoxia, a condition where the body does not receive enough oxygen. This can lead to dizziness, confusion, loss of consciousness, and even death.

4. How does nitrogen-rich air affect combustion in general?

In general, nitrogen-rich air will inhibit combustion. This is because nitrogen gas is non-reactive and does not support combustion. In high concentrations, it can even extinguish a fire by displacing oxygen.

5. Can nitrogen-rich air cause explosions or fires?

In most cases, nitrogen-rich air will not cause explosions or fires. However, if there is a high concentration of flammable materials present, the lack of oxygen in the air can create a combustible environment. Additionally, if nitrogen gas is rapidly released, it can displace oxygen and potentially cause an explosion if there is a source of ignition present.

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