This Blue Flame 20,000 BTU Natural Gas Vent-Free heater is the perfect supplemental heating solution even on the coldest days. This heater is conveniently equipped with a thermostat for superior control of the temperature in your space. Also, with a battery powered electronic ignition, starting it is a breeze - battery included. This unit can be permanently mounted to the wall or securely fastened to the floor with included mounting brackets and fasteners. A clean burning blue flame tube burner uses the natural convection of the burn to circulate warm comfortable air. With a factory standard Oxygen Depletion Sensor (ODS), rest assured this heater will provide you with years of comfortable and safe heat. Note: Check local code for permitted uses. Not for use in bathrooms, bedrooms, or recreational vehicles. 4,500ft high altitude restriction. Propane cylinder must remain outdoors.Convenient top-mounted comfort control adjustable thermostat