Why is positive-pressure ventilation used in the operating room?

• A. To prevent contaminant inflow from adjacent spaces
• B. To improve temperature control
• C. To save energy
• D. To reduce humidity

Answer: (A)

Maintaining higher pressure inside the operating room than surrounding spaces keeps contaminants from entering. Since air moves from higher to lower pressure, when doors are opened, clean, filtered air tends to flow out of the room rather than pulling in air from hallways or adjacent rooms. This helps keep the sterile field free from microbes and dust. The air in ORs is also HEPA-filtered and exchanged frequently to further minimize contaminants.

The other factors—temperature control, humidity, or energy savings—are important HVAC considerations, but they are not the primary reason for positive-pressure ventilation in the OR. In contrast, negative pressure is used to contain contaminants in other settings, so the positive pressure specifically protects the patient and sterile environment by preventing outside air from entering.