I bought one of these and it's the best investment ever for sniffing out gas leaks. It's very sensitive, but you can also adjust it so you can pinpoint the source of the gas by turning down the sensitivity as you move the thing closer to the leak source.
It sounds off like a Geiger counter with it's ticking getting faster as you get nearer to the leak source.
Works for batteries too; ever wonder how much hydrogen gas is coming off your batteries and if they are vented enough? This will tell you.
https://www.amazon.com/AGM-Detector-Combustible-Natural-Tester/dp/B00WMP9ZZW/ref=sr_1_12?ie=UTF8&qid=1511375228&sr=8-12&keywords=gas+sniffer![](https://images-na.ssl-images-amazon.com/images/I/51zugRnbFXL._SL1000_.jpg)