Depressurization

Depressurization is the reduction of pressure within a sealed or pressurized environment, typically resulting from a breach, venting, or deliberate release of gas. It creates a pressure differential with the surrounding environment and may occur rapidly or gradually.

Two main forms are recognized: rapid (catastrophic) depressurization and controlled (gradual) depressurization. Rapid depressurization involves a sudden loss of pressure due to a breach or rapid venting, while controlled depressurization occurs through valves or vents designed to relieve pressure over a period of time. Depressurization can affect entire vessels or individual compartments and may be partial or complete.

Common contexts include aviation, spaceflight, and industrial systems. In aircraft, cabin depressurization happens when the aircraft’s pressurized cabin loses integrity or when outflow valves malfunction, potentially leading to hypoxia and other physiological effects; procedures include donning oxygen and performing an emergency descent. In spacecraft and spacesuits, depressurization poses severe risks to crew, requiring redundant life-support and rapid isolation of affected areas. Industrially, depressurization is managed in pressurized pipelines, reactors, and vessels to prevent overpressure, with relief valves, vents, and monitoring systems designed to control the rate and extent of venting.

Causes range from structural failure and door or hatch breaches to valve faults, punctures, and deliberate venting for safety or process control. Effects of depressurization include rapid air expansion, temperature and condensation changes, equipment stress, and potential injury to people from hypoxia, barotrauma, or moving objects.

Mitigation focuses on robust design with redundancy, leak detection, and automatic pressure-relief mechanisms, alongside operational procedures and emergency response plans to minimize risk and ensure rapid restoration of safe conditions. Depressurization is therefore a key consideration in the design and operation of any system that relies on controlled internal pressure.