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Negative room pressure is an isolation technique hospitals and labs can use to control an environment where contaminants may be present. Airborne contaminants in the room will stay under control in a room with negative pressure, rather than leaking out into the rest of the facility. In hospitals, this is necessary for patient isolation rooms when patients have conditions like tuberculosis and could spread disease in a regular room or on an open ward. Labs can also rely on negative pressure rooms for securing some types of biological and chemical risks.
This concept relies on the fact that air will move from areas of high pressure to areas of low pressure. Air pressure wants to equalize itself, and the air will continue to move until the pressure stabilizes. With negative room pressure, the ventilation system moves air out more quickly than air can move in. This creates negative pressure and encourages air from halls and neighboring rooms to flow into the negative pressure room, rather than allowing contaminated air out.
Air cycles through a negative pressure room around 12 times an hour to keep it fresh and breathable. The air vented from the room moves through a filtration system that pulls out contaminants and vents the air safely into the surrounding environment. Many biological hazards are very sensitive to ultraviolet light, and will quickly break down as soon as the air vents into the outside. The negative room pressure ventilation system may vent to a roof or other infrequently trafficked area to ensure that everything breaks down before coming into contact with people who might be vulnerable.
With negative room pressure, it is very difficult for contaminants in a room to travel into the rest of the facility. Health care providers and researchers can move freely about the room and usually rely on a small anteroom between it and the surrounding environment to minimize disruptions to the pressure differential caused by opening and closing doors. After working in the room, it may be necessary to decontaminate, change garments, or take other steps to protect health and safety.
Patients in an environment with negative room pressure should not notice anything out of the ordinary. The ventilation system is discreet and will not disrupt sleep or conversations. The regular air changes keep the environment fresh, and filters may also treat the recirculating air. If the room starts to feel stuffy or close, this may be a sign that the ventilation system is not working properly, and a technician should evaluate it and make any necessary adjustments or repairs.