A dual fuel vent free gas heater having at least one gas burner with a plurality of gas outlet ports in an upper surface thereof. The gas outlet ports are in flow communication with at least one pilot flame burner. An adjustable fuel injector or at least two fuel injectors feed fuel to the burner providing for introduction of more than one fuel to the burner. Optionally, an oxygen detection system, manual fuel selection control valve, and/or temperature shut off control system may be incorporated into the dual fuel vent free heater.