Abstract: The invention incorporates a thermally responsive rotor, with a primer athed, that revolves to an ignition position upon influence of a temperature rise. Thermally sensitive actuators, also incorporated in the invention, are designed to respond to the temperature rise according to the rate of temperature change. The actuators serve to cock a spring loadable slide. This slide has a firing member nose that is aligned with the primer when the primer and rotor are rotated to the ignition position. At full cocking of the slide, the actuators and slide become disengaged and the slide springs towards the primer. Impact of the slide's nose with the primer causes the primer to be initiated, resulting in a venting or a venting and ignition of an energetic material.