SainSmart MQ2 DC 5V Propane Ethanol Gas Sensor Detection Module for LPG Propane Hydrogen Arduino Wide detecting scope, Fast response and High sensitivity, Stable, Simple drive circuit. Detection Zone:300 to 10000ppmm Characteristic Gas:1000ppmmIso-Butane Sensitivity:R in air/Rin typical gas5 Sensitive Resistance:1K to 20K in 50ppm Toluene