A method and apparatus for determining whether an appliance is leaking gas is provided. Pressure measurements are taken after closing off the flow of gas to the appliance and within the appliance so as to isolate the gas within the distribution system of the appliance. If unacceptable changes in the pressure of the gas are detected, a warning signal can be provided and the flow of gas into the appliance can be maintained in an off state until further corrective steps are undertaken. Corrections for temperatures changes between pressure measurements can also be provided.