Supplimental oxygen supply

[PPRuNeUser0179]

Good day all
Please excuse me if this is posted in the wrong forum but I was not too sure where a post like this would be posted.
Anyway...
I was having a discussion with a mate of mine last night about oxygen.He claims he read somewhere in a magazine that if a person were to breathe in pure oxygen,it would be fatal.
I do not believe this 100% but I suspect that if you were not trained to do this like ie:an astronaut,It would do some harm.
But Im busy studying for my Human Performance+Limitations exam which I am writing on Friday,and in the book,it says the following:From 10 000Feet to FL300 (you require additional OČ supply)
From FL300-FL400(you require 100% OČ)

So,if I am not wrong,most airlines that fly above FL300 use 100% oxygen for the passengers?
If not,do they mix the oxygen with Nitrogen/COČ?

Thanks very much everyone

[Dg800]

Oxygen does become toxic to the point of being fatal only at pressures somewhat higher than one atmosphere. This is a risk only to deep sea divers who use oxygen-enriched synthetic mixtures, up to 100% oxygen in closed-circulation systems, and not to airmen or passengers who only use oxygen at pressures that are inevitably substantially lower than 1013.12.

So,if I am not wrong,most airlines that fly above FL300 use 100% oxygen for the passengers?

Airliners have a pressurized cabin, both passengers and crew members are breathing normal air but at a higher pressure than what you find outside the cabin. The regulation you read only relates to unpressurized aircraft.

Ciao,

Dg800

[AvChappy]

As Dg mentioned, 100% O2 is only toxic with surrounding atmospheric pressures above normal, like SCUBA diving. Aircraft oxygen isn't normally taken in at 100% either, checkout diluter demand, pressure demand and continous flow. The only time a pilot would get 100% is if he selects that function on their mask