A direct fired system the airflow goes directly over the flame. An indirect fired air heater has a heat exchanger that the air passes over.

A great way to heat your warehouse and save 40%-70% on fuel consumption would be with a Cambridge “direct fire” roof mounted unit. This unit draws 100% outdoor air to heat your space and at the same time can pressurize your building to keep out cold air infiltration. See Cambridge unit in the Resource page to learn more.