I took this picture yesterday on a flight from Dallas Tx to Atlanta Ga.
Here's some interesting facts.
At 35000 feet the temperature is -68.72 and the pressure is 7.04.
Average Effective Performance Time for flying personnel without supplemental oxygen at 35000 feet is 30 to 60 seconds.
Up to approximately 35,000 feet, an aviator can keep sufficient oxygen in his/her lungs to permit normal activity by use of oxygen equipment that supplies oxygen upon demand (inhalation). The oxygen received by the body on each inhalation is diluted with decreasing amounts of air up to approximately 33,000 feet. Above 33,000 feet and up to approximately 35,000 feet, this equipment provides 100-percent oxygen. At approximately 35,000 feet, inhalation through the DEMAND oxygen system alone will NOT provide enough oxygen.