A ventilation system is necessary to maintain sufficient quality and quantity of the air in an underground mine. Intake refers to the fresh air or the fresh air handling system; the intake air is the clean air that is pumped into the mine from the surface.

As the intake travels through the mine, it can collect dust, gases, heat, humidity, and radiation. Return refers to this stale air or the stale air handling system. The return air is pumped out of the mine.

Figure: As shown, the air from the surface moving into the mine/ working section in known as intake, and the flow moving away from the section in called the return.