MQ-4

Detects methane and compressed natural gas, the sensor to fit where a building runs on piped natural gas rather than bottled LPG. Provides both an analogue output that tracks concentration and a digital output tripping at an adjustable threshold. Like all MQ sensors it needs one to two minutes of warm-up and draws around 150 mA continuously for its heater. It indicates relative concentration rather than a calibrated ppm figure — excellent as an alarm, not as an instrument. Specifically tuned to methane and natural gas; Analogue output plus adjustable digital threshold; Fast response suits leak alarm applications; Low sensitivity to alcohol and smoke reduces false alarms