The Spectrex SharpEye 40/40D-L4B is capable of detection Hydrocarbon fuel and gas fires and responds to flash fires in under 20 msec. The units work with an integrated UV and optical IR sensor in the 4.5 micron area. This allows for a higher false alarm immunity then other regular UV/IR models on the market and with this proven record of false alarm immunity they keep a SharpEye on your Safety!