Classicly

These notes were originally intended as a source of general reference concerning OXYGEN EQUIPMENT AND ITS USE by members of crews of the B-17 and B-24 heavy bomber. Through long hours of tiring training you have developed superior judgment, ability to make decisions quickly, and efficiently in firing and in other duties. Most of your training has been confined to relatively low altitudes in a relatively "normal" environment. Now you are going to continue this training "upstairs". To maintain the superiority and efficiency you possess OXYGEN MUST BE USED above 10,000 feet. Above 18,000 feet oxygen must be used to maintain consciousness and life itself.