Make up air is fresh outside air brought into a building through ventilating (heating or cooling) equipment.
Make up air that is supplied through displacement ventilation diffusers remote from the hood, perforated diffusers located in the ceiling as far as possible from the hood or as transfer air from the dining room generally works well if air velocities approaching the hood are less than 75 feet per minute (fpm). Make up air introduced in close proximity to an exhaust hood has the potential, however, to interfere with the hood’s ability to capture and contain. The chances of makeup air affecting hood performance increases as the percentage of the locally supplied MUA (relative to the total exhaust) is increased. In fact, 80% rule-of-thumb for sizing airflow, through a MUA unit can be a recipe for trouble, particularly if the exhaust flow rate has been over-specified to start with.
Please give C-Aire of Myrtle Beach a call if you need help with your make up air!