Detection: The mq136 / 137 / 138 / 139 sensors module set includes MQ136 ( H₂S), MQ137 ( NH₃), MQ138 ( HCHO), and MQ139 ( CFC) detectors, offering accurate detection ranges from 1-200ppm to 10 1000ppm for various hazardous High Sensitivity: Specifically designed for detecting H₂S, NH₃, HCHO, and CFC with reliability sensitivity, for indoor air and industrial leak detection Compact and Lightweight Design: Each module measures 20.4x32.4mm, made from durability ABS for easy integration into different systems Versatile Compatibility: Suitable for use in multiple environments including homes, and industrial plant, providing real time concentration for Wide Application: Ideal for environmental, industrial, and smart home systems, ensuring air and in settings like wastewater and agriculture, Manufacturer: HDOYTXXM