Infectious diseases and chronically ill patients require special air handling equipment in hospital isolation rooms. The isolation could dictate either positive or negative pressure in the room.
An isolation room at negative pressure has a lower pressure than that of adjacent areas. This keeps air from flowing out of the isolation room and into adjacent rooms or areas. In contrast, higher (positive) air pressure in the isolation room than in the adjacent corridor or anteroom prevents transmission from the outside environment to severely immunosuppressed patients.