Fire and breathing in nitrogen-rich air

[snorkack]

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?

 

[CWatters]

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.

 

[CWatters]

Also..
https://en.wikipedia.org/wiki/Hypoxic_air_technology_for_fire_prevention

 

[jim mcnamara]

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