Inficon AST 300 PPM Refrigerant Leak Detector with PPM Display (Model: AST300PPM)

Absolutely the best sniffer available! Had the pleasure of operating one of these at a former employer that deals in rack systems for grocers. You can be in your work vehicle, turn this thing on, walk through the door and it will literally walk you to the leak if one is present! We're talking from the front doors of (let's say) a walmart and if there is freon in the air. It will detect it in ppm. Is it pricey? Yes. But in my opinion it's hands down worth the money!