What is the purpose of make-up air?

• A. To replace exhausted air and maintain proper pressure and ventilation performance.
• B. To heat the building
• C. To humidify the kitchen
• D. To discharge smoke to outside

Answer: (A)

Make-up air supplies outside air to the kitchen space to replace the air that the exhaust hood removes. Its main purpose is to keep the space at the proper pressure and ensure the ventilation system operates as designed. If exhausted air isn’t replaced, the area can become negatively pressurized, which can draw in unwanted air, disrupt appliance operation, and reduce hood effectiveness. Make-up air is brought in in a controlled way—from a dedicated makeup air unit or dampers—and is often conditioned to maintain comfort and meet code requirements. This function is not about heating, humidifying, or discharging smoke; those tasks belong to other systems, while makeup air’s role is specifically to balance the air volume and pressure.