An essential training feature for Navy aviation cadets is to learn to live and fight in the thin of high altitudes. From the safety of the low pressure chamber, they get their first experience with the tricks which lack of oxygen can play on the human system, and with operation of their oxygen masks. Under the watchful eye of a Navy rating, a pharmacist's mate, or hospital corpsman, they "ascend" to 25,000 feet in the low pressure chamber at training school.