Section 108.407 - Detectors for electric fire detection system(a) Each detector in an electric fire detection system must be located where- (1) No portion of the overhead of a space protected is more than 3 meters (10 feet) from a detector;(2) Beams and girders extending below the ceiling of the space protected and any other obstructions do not detract from the effectiveness of the detector; and(3) Damage to the detector is unlikely to occur if it is not protected.(b) Each detector must be set to activate at not less than 57 °C (135 °F) and at not more than 73 °C (165 °F), except that if a space normally has a high ambient temperature each detector may be set to activate at not less than 80 °C (175 °F) and not more than 107 °C (225 °F).