Which statement best captures the commonly cited air-exchange requirement for operating rooms?

• A. 15 air exchanges per hour
• B. 5 air exchanges per hour
• C. 40 air exchanges per hour
• D. 25 air exchanges per hour

Answer: (A)

The key idea is how often the room’s air is replaced to dilute contaminants and protect the sterile environment. Air changes per hour (ACH) tell you how many times the entire volume of air in the operating room is refreshed each hour. A commonly cited minimum for general operating rooms is 15 air exchanges per hour. This rate helps dilute and remove airborne contaminants, including surgical smoke and bacteria, helping to maintain a clean field.

Higher rates (like 25 or 40 ACH) are not the standard baseline for most general ORs; they may be used in specialized setups, but 15 ACH is the widely referenced requirement for typical operating rooms. A much lower rate (such as 5 ACH) would not adequately dilute contaminants and could compromise the sterile environment.