• ID: mq4
• Name: MQ4 Methane and Connecticut Natural Gas (CNG) Sensor
• Category: gaseous
• Manufacturer: dfrobot
• Connection: analog
• Link: https://www.dfrobot.com/index.php?route=product/product&product_id=683

The MQ4 Gas Sensor module is useful for detecting CH4 (Methane), and natural gas concentrations in the air. It has a detection range of 100-10000 ppm.
For optimum use, it requires calibration after a pre-heat time of at least 24 hours. See the datasheet for details.