Gravity analogue hydrogen gas sensor (MQ8) for Arduino has high sensitivity to hydrogen (H2) and less sensitivity to alcohol, LPG, cooking fumes. Hydrogen gas is highly flammable and will burn in air at a very wide range of concentrations. The sensitivity is able to be adjusted by the potentiometer. The output is proportional to the density of gas. Users can use analogue reading to read the data from this sensor. To ease the difficulty of using this sensor, a gravity Interface is adapted to allow plug&play. The Arduino IO expansion shield is the best match for this senor connecting to Arduino microcontroller.