Description

Gas sensors are electronic components that can easily detect different kinds of gases. The series of gas sensors compatible with Arduino is called the MQ series. The most commonly used sensor from this series is the MQ2 Gas sensor. This is because the MQ2 can detect a wide variety of useful gases and can be used in projects like gas leak systems etc. They are generally used with a buzzer or alarm of some kind. Below you will find the list of MQ sensors that are available to use with the Arduino and the gases it can detect.

• MQ-2: Methane, Butane, LPG, Smoke.
• MQ-3: Alcohol, Ethanol, Smoke.
• MQ-4: Methane, CNG. 
• MQ-5: Natural gas, LPG.
• MQ-6: LPG, Butane gas.
• MQ-7: Carbon monoxide gas.
• MQ-8: Hydrogen gas. 
• MQ-9: Carbon monoxide, flammable gases. 
• MQ131: Ozone.
• MQ135: Carbon monoxide, Benzene, Ammonia, Alcohol, Smoke.
• MQ136: Hydrogen Sulfide. 
• MQ137: Ammonia. 
• MQ138: Benzene, Toluene, Alcohol, Acetone, Propane, Formaldehyde, Hydrogen.
• MQ214: Methane, Natural gas.

When measuring gases, the concentration of such gases is measured by the amount of gas by volume in the air. The most common units of measurement for this are parts-per-million and percentage concentration. For instance, if the concentration of CO gas in an environment is 1000 ppm, then there are 1000 molecules of CO gas in one million molecules of air.