Make-Up Air Calculator

The Make-Up Air Calculator is used to determine the volume of make-up air (MUA) required to replace air exhausted from a building or space. This is crucial in environments with significant exhaust systems, such as commercial kitchens, laboratories, or industrial facilities, to maintain proper building pressure and indoor air quality. The calculator typically requires the total exhaust airflow (CFM) and a desired make-up air percentage (e.g., 80-100% of exhaust) to calculate the necessary MUA volume. Proper MUA design prevents issues like negative pressure, backdrafting of combustion appliances, and poor exhaust fan performance.

Consequences of Inadequate MUA: Failing to provide adequate make-up air can lead to severe problems. Negative building pressure can cause drafts, make doors difficult to operate, and pull unfiltered air through cracks and openings. More critically, it can cause backdrafting of combustion appliances like furnaces and water heaters, potentially drawing dangerous flue gases (including carbon monoxide) into the building. Exhaust fan performance is also reduced if they are starved for air.