Locate the burner output adjustment knobs on the antique Kenmore gas room heater. They will be located on the back of the heater or underneath the heater’s firebox. There will usually be more than one knob. Each knob controls a corresponding burner orifice inside the heater.
Turn the gas valve to the "On" position on the back of the heater. The gas valve is located where the gas line attaches to the heater. Hold the pilot knob down on the back of the heater until it clicks and turn it to the "On" position in order to light the room heater's burners. The pilot knob is the largest knob on the back of the heater.
Turn the burner knobs to the left to make the flame larger. Turn the burner knobs to the right to make the flame inside the heater smaller.