Positive pressure means an area or room has a higher pressure than the space around it. Because they are designed to keep out contaminants, positively pressurized rooms are among the cleanest spaces in a hospital and are used to protect the patients most vulnerable to airborne infections. If there is a leak or open door in a positive pressure room, clean air is forced out rather than contaminated air let in.
Positive pressure can be used in conjunction with negative pressure to ensure airborne contaminants do not enter or escape a space, such as an anteroom next to an isolation room. Positive pressure also helps maintain sterility in areas like operating rooms and supply closets.