Detecting the occurrence of the fireball at its incipient stage, when size and energy emitted by it are small enough to be controlled by suppression, is a critical factor in automatic fire protection systems. An electro-optical sensor is the quickest means to identify a fire. A special UV/IR combination provides greater sensitivity and higher speed of response while providing a high immunity to false alarms.  IR3 optical detectors are suitable for use in the engine compartment of military vehicles as well as for fire detection outside the vehicle.