Mr. Heater 25,000 BTU Radiant Natural Gas Workshop Heater HS25N25,000 BTU Mr. Heater Radiant Natural Gas Workshop Heater HS25N Product Details 99. 9% Fuel Efficient. That is what the Heatstar 25,000 BTU Natural Gas radiant heater offers. Whether you use it in your garage to keep your cars warm, in your shop to keep the work force busy and comfortable, or in a poultry house eggroom, the Heatstar radiant heater transfers almost all of the fuel it burns directly into clean, safe radiant heat. Utilizing a unique