The MQ-2 Gas Sensor with Sensor Modules ROHS manufactured by Waveshare is a gas sensor that is used to detect combustible gases and smoke in the environment. This device has a high sensitivity and wide measuring range to detect flammable combustible gases such as LPG, natural gas, coal gas, methanol, propane, etc. Additionally, it is also suitable to detect the smoke generated during fires. The module can be powered by 5V DC and requires a small amount of current in order to operate. The detected gas concentration is displayed as analog output voltage which can be adjusted with a potentiometer. It includes an LED which indicates when the gas concentration has exceeded the threshold levels. The device is also RoHS compliant and is designed for easy integration into other electronic circuits and systems.