Pressure Chamber

a hermetically sealed chamber for decreasing pressure (vacuum chamber) or increasing it (compression chamber). The most common pressure chambers are those of decreased pressure, in which the pressure may be changed from that of the earth’s surface to fractions of mm of mercury (1 mm of mercury = 133.322 newtons/m²). The volume of the chamber may range from a fraction of a cubic meter to several hundred cubic meters, depending on its purpose. The pressure chamber is equipped with special apparatus for changing the pressure, for maintaining it at a prescribed level (vacuum pumps with a system of regulation, a mercury manometer, altimeter, and so forth), and for changing or maintaining the composition of the air. Depending on their purpose, some chambers contain devices for changing pressure at definite speeds, making it possible to imitate ascent or descent, and special systems for signaling, control, communication, and so forth. Pressure chambers in which temperature may be changed simultaneously with pressure are called thermal pressure chambers; they are equipped with devices regulating temperature.

Pressure chambers are widely used in research and for calibrating aviation, meteorological, aerological, and other instruments containing elements that measure pressure. They are used for testing airplanes and airplane engines, for training flight crews and cosmonauts, for studying the effects on living organisms of hypoxia, decreased or increased barometric pressure, abrupt changes in pressure, changes in the gaseous atmosphere, and for other purposes. In medicine they are used in the treatment of such diseases as whooping cough, bronchial asthma, and the bends (caisson disease) and in some operations (for example, open heart surgery).