This sensor is a part of gravity series by DFRobot
DFRobot Gravity Series is a high quality open-source, modular, plug and play electronics toolkit for everyone to create anything easily. Gravity Series allows users of any skill level to easily connect and mix to realize ideas or develop projects.
Specifications
Power supply needs: 5V
Interface type: Analog
Pin Definition:  1-Output  2-GND  3-VCC
High sensitivity to LPG, natural gas, town gas
Small sensitivity to alcohol, smoke
Fast response
Stable and long life
Simple drive circuit
Size: 40x20mm(1.57″x0.79″)