The new HIF 690 and HIF 1200 flameless indirect-fired heaters use a diesel engine to generate heat, so the flame is completely isolated from the surrounding environment. Cool, ambient or recirculated air is drawn into the heater body and pullted through an exhaust heat exchanger, where it achieves signifcant heat gain. Air temperature increases further as it is drawn across the engine and heat plate. Wacker Neuson. WOC Booth O30145