This Blaze 200 model is a diesel indirect-fired portable heater that puts out 300,000 BTU's and features "Four Pass Heat Exchanger Technology" which allows exhaust gases to increase heat exchange with the cooling air to obtain maximum thermal efficiency. The heat exchanger contains the flame and expels fumes that can be ducted outside or released through the chimney. These super-efficient indirect-fired heaters can be operated indoors and can also be ducted. It is Ideal for heating large spaces, such as your warehouse, or where suspended dust particles must be avoided.