method and apparatus are provided for minimizing delay in the operation of a safety device in a device for thermally fixing an image to a paper medium . a safety device , such as a thermostat , is set to deactivate a heater unit if the temperature of the heater unit exceeds a first temperature value . if the temperature of the thermal unit exceeds a second temperature value lower than the first temperature value , a heat exhausting device , such as a fan , is turned off . shutting off the heat exhausting device stops cooling of the heater , thus decreasing the time elapsed before the safety device can detect the first temperature value .