Positive pressure

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Positive pressure is a pressure within a system that is greater than the environment that surrounds that system. Consequently if there is any leak from the positively pressured system it will ingress into the surrounding environment.

However, use is made of positive pressure to ensure there is no ingress of the environment into a supposed closed system. A typical example of the use of positive pressure is the location of a habitat in an area where there may exist flammable gasses such as found on an oil platform.

Hospitals may have positive pressure rooms for patients with compromised immune systems. Air will flow out of the room instead of in, so that any airborne germs that may infect the patient are kept away.

Amphibians use this process to respire, whereby they use positive pressure to inflate their lungs.

See also: negative pressure, plenum.