1.adopt NDIR theory 2. small size 3.4 series ndir sensor 4.detection range:0-5%vol/0-100%LEL 5.best price Infrared SensorMH-440V/D1. IntroductionMH-440V/D infrared gas sensor is a miniature universal intelligent sensor, which adopts NDIR theory to detect concentration of CH4 in air and has good selectivity, stable performance, long life, also is independent of Oxygen. The inside temperature ...