Crew oxygen
 

I have 2 questions regarding crew oxygen:

Since during a preflight we put Normal/100% switch to 100%. Under what circumstances we use the Normal (air-oxygen mixture)?

also the Emergency selector states that it provide 100% under positive pressure. Does this mean it is a “continuous flow of oxygen”?

thanks

Yes, that is correct.

In the "EMER DESCENT" Abnormal Procedure PRO-ABN-MISC, it says go to "Normal" to preserve O2 supplies.

If you are over high ground, European Alps, Mongolian Plateau etc the time to 10,000ft may be longer than normal so preserving O2 is a factor.

It's a demand respirator as far as type of mask it is... flights requiring escape route or extended time over high terrain will be required to carry more O2

Gotcha thank you so much guys