The Grove - Gas Sensor module is useful for gas leakage detecting(in home and industry). It can detect LPG, i-butane, methane, alcohol, Hydrogen, somke and so on. Measurements can be taken as soon as possible based on its fast response time. Also the sensitivity can be adjusted by the potentiometer.
There are different gas detectors for sale, like MQ2, MQ3,MQ5andMQ9. Below is a contrast table of them.