Abstract: A safety device for a combustion apparatus comprises a continuous, linear temperature-sensing element formed of a material which is electrically conductive and melts, or breaks, at a relatively low temperature and located along at least one side of a combustion chamber of a combustion apparatus and one side of a heat exchanger thereof. The temperature-sensing element is electrically connected to a combustion control circuit such that, if and when the combustion chamber or the heat exchanger has reached an extremely high temperature, the temperature-sensing element melts, or breaks to cause said combustion control circuit to stop a combustion in said combustion chamber. Lead, tin, or an alloy of lead and tin may be employed as the material of the temperature-sensing element.