is derived from a 460 volt 3 phase alternating power source through the transformer 118 the circuit includes ground detection devices 120 and stop 122 and start 124 switches for the incinerator blower 98 the blower 98 is provided with separate 3 phase 460 volt power 126 as shown and is energized by the relay m 1 upon actuation of the start switch 124 the initial actuation of the blower purges the incinerator with fresh air before firing can be initiated actuation of the start switch 124 also energizes the circuit through the air pressure switch 108 and high limit control 114 as shown thus failure of sufficient air from the blower or an over temperature in the incinerator will completely shut down the ignition and operational controls for the gas supply to the incinerator and prevent gas from entering through either the pilot valve 92 or main gas valve 90 subsequent to starting the blower the ignition switch 128 is actuated thus energizing a thermistor network 130 and electronic network 132 the thermistor network 130 actuates relay 1k to open the pilot valve 92 and energize the ignition transformer 134 and spark plug 136 thereby igniting the fume heater 84 flame sensing means 138 upon a proven flame cause the electronic network 132 to energize the relay 2k which in turn disconnects the ignition transformer 134 and energizes the circuit to relay 1 cr and energizing the temperature controller 110 the temperature controller is set at the proper operating temperature which will be maintained regardless of the fume quantity drawn into the.