RDG006001 The Institutes low pressure chamber has a broad range of applications in both basic research and the development of new systems. Here, an environmental stress subject is being weighed underwater during a rapid ascent to the simulated altitude of 18,000 feet, to determine his increased buoyancy due to the reduced barometric pressure. This measured weight loss will be used as a factor in the determination of air-free body weight, or specific gravity. Because of the short time that the chamber is kept at a reduced pressure, the personnel do not require oxygen masks.