The Universal Cab Heater, i.e. the HC Heater, you have purchased is a thermostatically controlled propane heater. It is designed to be mounted on the inside of the cab of heavy equipment or inside a small building.
It is a heavy duty forced air heater with electronic ignition. To maximize safety, the combustion air is completely separate from the inside air. The combustion air is drawn from the outside, burnt with propane, heat exchanged to warm the inside air, and exhausted outside the sealed heating area.