What Is Negative Room Pressure?
Negative room pressure occurs when exhaust airflow exceeds supply airflow, creating lower air pressure that allows external air to flow inward while preventing interior air from escaping. This is valuable in medical settings for isolating patients with infectious diseases.
Testing Negative Room Pressure
Visual assessment using a smoke capsule or tissue outside the door reveals airflow patterns. Electronic monitoring with continuous pressure monitors measures differential air pressure precisely.
Negative-pressure isolation rooms require a minimum of 12 air changes per hour and must maintain minimum 0.01-inch WC negative-pressure differential.
Room Integrity
Proper room construction is critical. Unsealed areas above drop ceilings allow air infiltration, undermining design calculations.
Common Negative Pressure Rooms
ER and radiology waiting rooms
Airborne infection isolation rooms
Laboratories and research facilities
Autopsy rooms
Decontamination rooms
Soiled workrooms
Bonus: Positive Pressure
Positive pressure rooms exhaust less air than supplied, protecting immunocompromised patients and sterile environments like operating rooms, delivery rooms, and pharmacy areas.