Abstract: A method and apparatus for controlling a fuel-fired appliance is provided. The appliance enters a wait state in which burner operation ceases if a sensor indicates the presence of flammable vapors that are above an acceptable and/or safe vapor level. The appliance returns to a run state if the vapor level returns to an acceptable and/or safe vapor level within a period of time, but enters a lockout state if the vapor level does not return to an acceptable and/or safe vapor level within the period of time.

Abstract: Vapor sensing systems and methods are disclosed. An appliance such as a gas water heater, clothes dryer, and the like can be associated with a controller for controlling the appliance. A vapor sensor is also associated with the appliance, such that the vapor sensor comprises an active sensor and an error sensor, wherein the active sensor generates an active signal and the error sensor generates an error signal. An amplifier is also associated with the vapor sensor, such that the amplifier subtracts the error signal from the active signal to generate a compensated signal indicative of the presence of an ignitable vapor within a vicinity of the appliance and thereby instruct the controller to shut down the appliance.