All cabin air volume is recirculated and exchanged in how many minutes?

• A. 1-2 Minutes
• B. 3-5 Minutes
• C. 10-15 Minutes
• D. 20-25 Minutes

Answer: (B)

Air in the cabin is constantly being refreshed by the environmental control system, which blends fresh outside air with recirculated cabin air that has been filtered. The recirculation helps conserve energy, while HEPA filtration removes particulates from the air before it’s reintroduced into the cabin. Because the system moves a large volume of air continuously, the entire cabin air mass is exchanged on the order of a few minutes—about three to five minutes under normal operating conditions. This corresponds to roughly twelve to twenty air changes per hour, which is how cabin air quality is maintained during flight.