Expert: Colin Woehrle - 8/20/2006

Question
My question is four-fold.  At what altitude and circumstances is oxygen required in GA flight, is there an altitude or circumstance above which a pressurized cabin is required, to what "altitude" is a cabin pressurized i.e. sea level, 8000 ft. and finally, what are the first physiological effects of oxygen deprevation i.e. a feeling of suffocation, urge to fall asleep, and the time to their onset from first exposure.

Answer
Hi Dan!


For GA flight:
1. Anytime you fly over 12,500ft above mean sea level (MSL) up to and including an altitude of 14,000ft. MSL in an unpressurized airplane for more than 30 minutes, oxygen is required for the crew-members. Oxygen is also required for the crew above 14,000ft MSL. At and above 15,000ft MSL oxygen must be PROVIDED to all passengers.

2. There is no regulation that I am familiar with that requires a pressurized cabin. Physiologically speaking however, just as an example, if a person were suddenly exposed the atmosphere at 30,000ft MSL without a pressurized cabin or at least a pressure-demand oxygen mask that supplies oxygen to the lungs via high pressure, hypoxia would set in in 45 to 75 seconds, followed by unconsciousness and eventually death.

3. Pressurized aircraft cabins are pressurized to different altitudes depending on the actual altitude of the aircraft. The maximum cabin altitude that airplanes can pressurize to is typically 8,000ft however.

4. The first symptoms of hypoxic hypoxia (insufficient oxygen available to the body) are unique to different people. General symptoms include tingling sensations around the face and fingers, cyanosis (blue lips, fingers, etc.), headaches, fatigue, shortness of breath, and nausea.

Hope this info helps you out! Sorry for any punctuation or grammatical errors- it's getting late! Thanks for the questions.

Sincerely,

Colin Woehrle