Patent ID: 7581946

Claim:
A control for controlling the operation of a fuel-fired heating appliance, the control comprising: a CO sensor disposed on the control in the vicinity of the appliance so as to ensure that the CO sensor is capable of sensing the presence of carbon monoxide gas and providing an output that changes relative to changes in carbon monoxide level so as to be indicative of the level of carbon monoxide gas, wherein said CO sensor is subject to changes in output value due to the effects of humidity or general aging; a memory in which one or more previously sensed sensor output values are stored; and a processor that monitors the CO sensor and stores at least one previously sensed sensor output values in the memory, and responsively discontinues the operation of the appliance when the CO sensor output increases by more than a predetermined amount of at least 50 percent over said at least one previously stored CO sensor output value, such that the control is configured to overlook any drift in the output value within 15 to 90 minute period of the sensor that might indicate an inaccurate level of carbon monoxide gas.