Negative pressure
Negative pressure is pressure less than that of the ambient atmosphere. Negative air pressure within a room will cause air to flow into the room from the outside whenever a door or window is opened. It is often used in the hospital setting to quarantine people afflicted with highly contageous, deadly, airborne diseases.Negative pressure is also often found in sub-sea pipelines where the depth of water produces such a high external pressure that any leak would actually be from the sea water into the pipeline.
Negative pressure is the opposite of positive pressure.
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