MQ series sensor uses a small heater inside with an electrochemical sensor in order to measure a different kind of gases combinations. They can be calibrated, but, in order to do that, a known concentration of measured gas or gases is needed. The MQ-8 hydrogen gas sensor is suitable for sensing hydrogen concentrations in the air. The MQ-8 can detect hydrogen gas concentrations anywhere from 100-10000ppm. This sensor has a high sensitivity and fast response time.