This is the MQ 06 Module Board Concentrated Petroleum, IsoButane, Propane, LPG Gas detection sensor detects from 300ppm to 10000 ppm, a range for detecting leak GAS. This sensor works on Analog input to your Arduino board. The MQ-6 detects concentrated gas from ground to air and outputs it reading

This is the MQ 06 Module Board Concentrated Petroleum, IsoButane, Propane, LPG Gas detection sensor detects from 300ppm to 10000 ppm, a range for detecting leak GAS. This sensor works on Analog input to your Arduino board. The MQ-6 detects concentrated gas from ground to air and outputs it reading as an analog voltage and operates at 50 degree Celsius, consumes less than 150 mA at 5v.Parameters:

• Voltage: 5v DC
• Dual Signal Output( TTL level and Analog)
• TTL Output valid signal for low level (When the low output electric signal lights at 4. Can be directly  pic up SCM)
• Works on Analog 0 to Analog 5 on 5v volts DC, the higher the concentration, the higher voltage consumes.
• High sensitivity to hydrogen GAS
• Can be resistant to Ethanol Steam, LPG Petroleum, and Smoke interference.