The Quad-Sense technology uses four independent IR sensors all placed in the invisible infra-red spectrum to detect hydrocarbon fires. Using this technology Spectrex creates an enhanced performance, advanced long-distance detection of hydrocarbon fires up to 300 ft (90 m), ultra-fast detection in under 50 msec with unparalleled reliability. The 40/40D-I ensures superior performance with immunity to false alarms while keeping a SharpEye on your safety!