Nonpressurized

Nonpressurized describes equipment, vessels, or systems that operate at ambient atmospheric pressure and are not designed to contain or maintain higher internal pressures. In practice, nonpressurized configurations rely on surrounding air for pressure balance and typically lack the structural reinforcement and safety features required of pressure vessels.

In aviation, nonpressurized aircraft have cabins that are not sealed against outside pressure. Passengers and crew experience outside atmospheric pressure, which limits altitude and typically reduces comfort and fuel efficiency. Such aircraft are lighter and cheaper to operate but cannot climb above certain altitudes without significant performance penalties.

In water systems and packaging, nonpressurized means lines, tanks, and channels rely on gravity or natural pressure differences rather than active pumping. Gravity-fed water systems use open or vented tanks and rely on elevation differences to create flow. Open-top storage vessels vent to the atmosphere, and pipelines lack pressure-rated design features.

In industry, nonpressurized reactors or storage vessels operate at or near ambient pressure and do not require pressure-relief systems unless external hazards are present. They are generally simpler and cheaper but more vulnerable to vaporization, contamination, or atmospheric ingress, and require appropriate containment for weather and dust.

Design and safety considerations: even nonpressurized equipment may vent, seal, or tolerate some pressure changes; materials should resist corrosion; components such as relief devices may be omitted when not needed.

See also: pressure vessel; ambient pressure; open system; gravity-fed network.