Heatstar PRO-SERIES 400,000 BTU/HR Indirect Fired Heater. The HSP500ID-A is an ideal heating solution for any large Industrial or rental application. Unit ships with factory installed dual 12" duct adapters. When paired with up to 100 ft of Heatstar high quality high temperature ducting, this indirect fired heater is an ideal heating system for delivering even heat to both event tents and construction sites with clean fresh heated air. You can place the unit outside the space and duct the warm air in or for a fuel savings you can place the heater in the space to be heated and vent the exhaust out. Either way it is hard to beat the comfort and safety of indirect heat.