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Old 15th Oct 2010, 15:20
  #696 (permalink)  
Daermon ATC
 
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Originally Posted by Jet Jockey
Regardless of altitude the percentage of oxygen in the air remains at 21%.

So depressurizing an aircraft at altitude will have no effect on snuffing out a fire.

A fire will sustain itself with an oxygen content down to 16%.
The fact you present is correct although I believe the conclusion is not.

Following the same reasoning, a human needs 21% oxygen to breath, therefore we should all breathe easily at FL450 since as you correctly state the percentage remains the same.

However the density does not and there are less molecules of oxygen available per cubic meter the higher you get up. Therefore the recommendation to depressurize the aircraft which should work with all fires except those providing their own oxygen for combustion.
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