Definition - What does Positive Pressure mean?
Positive pressure refers to pressure that exceeds the surrounding pressure of any room, chamber or confined space. Positive pressure is maintained in a closed zone to ensure no outside contaminated gaseous or liquid substance can get into that protected zone.
Safeopedia explains Positive Pressure
Positive pressure ensures no ingress of outside substance into the protected zone. In case there is a leak in the encircling wall, screen or membrane, the inside substances egress to the surrounding area. Positive pressure is maintained in many places such as in the inside of an aircraft, in naval ships passing through a nuclear, biological or chemical contaminated area, or inside the masks of a breathing apparatus such as that used by firefighters. Our blood system is also kept at positive pressure by nature, to prevent germs from entering into our bodies through a cut or injury.
Positive air pressure clean rooms are used by electronics, aerospace, optics, military and defense applications and researchers. In these rooms, the air escaping from doors, ceilings or walls, due to the positive air pressure is not harmful.