In a negative air pressure environment, what is the term for the additional air source that refills the space?

• A. Return air
• B. Fresh air
• C. Exhaust air
• D. Makeup air

Answer: (D)

When a space is under negative pressure, air is being pushed out of the room and must be replenished from outside to maintain the required pressure differential. The air that refills the space is makeup air. It serves to offset the air removed by exhaust and leakage, helping keep the room at the intended negative pressure and ensuring contaminants don’t migrate to adjacent areas. Makeup air is typically outdoor air that may be conditioned and filtered as needed before entering the space. In contrast, return air is air that’s already circulating back to the HVAC system, and exhaust air is the air leaving the space. Fresh air is a general term for outdoor air, but the specific term for the air that refills a negative pressure space is makeup air.