pressurization

Pressurization is the process of maintaining a controlled, higher or lower ambient pressure inside an enclosed space than the surrounding environment, by regulating the amount of gas that enters or leaves the space. It relies on a pressure vessel capable of withstanding differential pressure, a supply of breathable gas, and a control system that adjusts inflow and venting to keep the desired cabin or room pressure. Pressurization is used to preserve comfortable breathing conditions, preserve equipment performance, and manage structural loads on enclosed habitats at high altitude or deep underwater.

In aviation, pressurization maintains a safe cabin environment during flight at altitudes where the outside air is too thin to breathe. An environmental control system blends conditioned air, provides temperature and humidity control, and uses an outflow valve and pressure controller to sustain a typical cabin altitude around 6,000–8,000 feet with a corresponding differential pressure of about 6–9 pounds per square inch. Bleed air from the engines or electrically driven compressors provides the supply; the system monitors cabin pressure and can initiate an emergency descent if necessary.

In spacecraft and submarines, pressurization serves similar purposes inside a life-support habitat where the external environment is hostile. Spacecraft use closed-loop life-support systems to maintain breathable partial pressures and protect crew, while submarines must withstand high ambient water pressures with a robust hull. In cleanrooms and hospital isolation rooms, positive or negative pressure differentials are used to limit the ingress or escape of contaminants, protecting products or patients.

Safety and design considerations include ensuring structural integrity to tolerate differential pressure, monitoring for rapid decompression, providing emergency oxygen and masks, and implementing failsafes and procedures for valve or system failures. Improper pressurization can lead to hypoxia, decompression sickness, or equipment damage.