Abstract: An improved radiant heater for use in dusty environments and at low gas pressures. An open throat, single port burner, which is not subject to obstruction in dusty environments, directs combustion products vertically from a lower fuel input end to an upper flame-emanating end. The burner is adjustably mounted to a base unit so that air entrainment into the burner may be controlled by adjusting the distance between the base unit and the burner fuel input end. The burner conductance may be adjusted to operate at varying fuel input fluxes by attaching an area reduction means to the burner. The burner flame emanating end is directed into a combustion chamber which absorbs the heat generated by combustion and radiates the absorbed heat into the ambient. The lower surface of the combustion chamber has an aperture for receiving the burner flame emanating end, and acts as a heat shield. Control components, such as control circuitry and a fuel valve, are housed within the base unit, further shielding them from heat.