CISNO Refrigerant Halogen Leak Detector A/C R134 R410a R22 Air Gas HVAC Tool Detects all HFC (134a) CFC refrigerants. Audio 'siren' and visual LED light alert when leak is found. Excellent sensor with high sensitivity, 6g/yr (0.2oz/yr). Re-set function enables you to set the meter to ignore ambient concentrations of halogen. Check your entire refrigerating system including the fittings, house to line couplings, controllers, service parts, the areas around the points of attachment, hold downs on lines and components.