Eathtek Replacement Portable Freon Halogen Refrigerant Gas Leak Detector Tester with High Sensitivity 7-level leak alarm R134a R410a R22 R12 HVAC Tools 0.1oz/yr Excellent sensor with high sensitivity, 0.1oz/yr (3g/yr) Detects All KINDS OF halogenated refrigerants Operate the leak detector according to the instruction manual. Switch off the machine after use. Remove batteries when unused for a long time, so that it could prolong life time. To ensure the high sensitivity, make sure the tip and protector is clean before using everytime.