Abstract: A low pressure heater control system. In some embodiments a control is in electrical communication with a sensor having a view of a combustion chamber. The control calculates an average sensor value over each of a plurality of brief sampling periods based on a plurality of readings from the sensor. In some embodiments a reference point that may be at least based in part on an average of a plurality of average optical sensor values from earlier brief sampling periods is calculated and compared against the average optical sensor value from a recent brief sampling period to monitor for an abrupt combustion change. In some embodiments a peak-to-peak optical sensor value is also calculated over each of a plurality of brief sampling periods. In some embodiments the type of fuel being combusted is recognized and/or the fuel level approximated based on measured average and/or peak-to-peak optical sensor values.