MQ-4 gas sensor sensitive material used in clean air conductivity is lower tin dioxide (SnO2). When the sensor is present in the environment in which the combustible gas, the sensor's conductivity increases with the concentration of combustible gases in air increases. Using a simple circuit can be converted to the change in conductivity of the gas concentration with the corresponding output signal. MQ-4 methane gas sensor for high sensitivity, propane, butane and has a good sensitivity. The sensor can detect a variety of flammable gases, especially natural gas, is a low-cost sensors for a variety of applications.

Specifications:

• Input voltage: DC5V power (current): 150mA
• DO output: TTL digital 0 and 1 (0.1 and 5V)
• AO output :0.1-0 .3 V (relatively clean), the highest concentration of voltage around 4V
• Dual-way Signal Output, Analog output and TTL level output High sensitivity to LPG, gas, alcohol, hydrogen and more
• Fast response and recovery
• Use for Detecting: Combustible gas such as LPG, butane, methane, alcohol, propane, hydrogen, smoke, etc.
• Detecting Range: 300 to 10000ppm
• Size 32X22X27mm 
• Special note: The sensor is powered, needs to warm up around 20S, measured data becomes stable, the sensor fever is a normal phenomenon, because the internal heating wire, if hot is not normal.