Mr. Heater MH18B, Portable Propane Heater 4,000- to 18,000-BTU radiant heater for spaces up to 450 square feet. Approved for indoor/outdoor use; clean-burning; nearly 100-percent efficient When operating the heater at altitudes over 7,000 FT above sea level the heater may shut off. Auto shut-off if tipped over, if pilot light goes out, or if detects low oxygen levels Low, medium and high heat level control knob for steady temperatures; connects to propane tank (not included) THE USE OF UN-AUTHORIZED ACCESSORIES/ATTACHMENTS WITH THIS HEATER ARE EXPRESSLY PROHIBITED, MAY CAUSE SERIOUS INJURY, AND WILL VOID THE WARRANTY.