Industrial Make-Up Air Units and How They Work

Industrial Make-up air units (MAU) introduce fresh supply air into the building to make up for air lost through exhaust fans and vents. This ensures that a large industrial facility maintains an even, uniform temperature without any cold zones or hot spots. This increased airflow also helps maintain proper pressurization and air flow — a factor we cover in more depth in the importance of make-up air.

Instead of recirculating already in the building like an air turnover unit, (Moffitt MAT) an MAU (like the Moffitt MMA) introduces clean, cool air from outside of the building. This fresh air improves worker comfort and health, contributing to a better working environment.

Make-Up Air and Heating Systems

MAUs, in addition to providing intake air, can also be fitted with key accessories like filters, evaporative cooling systems, and heating units. These heating systems warm the fresh incoming air to ensure that the building stays comfortable even in winter.

Specifically, make-up air units use two main types of heaters.

Direct Fired Heaters

Direct fired heaters push the incoming air directly through a flame. Think of this as a putting a fan over a gas stove top. This ensures that the air coming into the building stays at an appropriate temperature during the winter. This process is powerful and incredibly efficient.

Indirect Fired Heaters

Comparatively, an indirect fired heater is more like a gas burning furnace with a chimney. The burn chamber contains the flame, which in turn warms a “heat exchanger”. The cooler air is warmed up as it passes over and around the heat exchanger. An indirect fired heater provides clean, dry air into the building. The circulated air never comes into direct contact with the flame. In this configuration the air stays as fresh and clean as it is outside. The dryness of the air from an indirect fired heater also prevents mold and mildew build-up.