The MP135 / MP503 Gas Sensor is a compact metal-oxide semiconductor sensor designed for air-quality monitoring and gas detection, with good sensitivity to methane. It features fast response and recovery, low power consumption, good stability, strong anti-interference capability, and long service life. The sensor’s conductivity changes with gas concentration, allowing a simple external circuit or microcontroller to measure the variation. It is suitable for Arduino, IoT, gas detection, environmental monitoring, and DIY electronics projects.