Abstract: Flue-gas analysis safety apparatus 10 for a gas or oil-fired device 30 having an electrical connection and a flue 54 for combustion gases, comprises a hazardous gas detection element 12 for placement in the flue 54 to monitor flue gas, and a controller 14 for automatically regulating a gas to air ratio in the flue gas based on a signal from the hazardous gas detection element 12. The controller 14 is able to halt a flow of electricity to the gas or oil-fired device 30 if the gas to air ratio in the flue gas cannot be regulated to fall within a predetermined safe parameter. Preferably, the hazardous gas detection element 12 includes a wireless transmitter, and the controller 14 includes a wireless receiver so that the hazardous gas detection element 12 is wirelessly communicable with the controller 14. A gas or oil-fired device having the apparatus 10, and a method are also provided.