Understanding how to use a refrigerant leak detector is as important as having one. Different sensing technologies required different methods of use and application. Heated Diode leak detectors trigger on an absolute concentration of refrigerant. Simply put, as you move closer to the leak, the audible and visual indication increase in frequency because more refrigerant is passing the sensor. IR (infrared) detectors detect refrigerant by sampling in a sweeping motion to pinpoint refrigerant leaks. IR sensors zero out of held over a leak. The advantage for IR is it triggers the same for all refrigerants unlike heated diode which work better then some refrigerants than others.