All About MQ Series Gas Sensor

What is a Gas Sensor?

Determining leakage is crucial in industries, residences, and workplaces since dangerous gases harm the environment. A typical human nose has 400 scent receptors, allowing humans to detect over 1 trillion different odors. But most of us cannot determine the kind or quantity of gas in our atmosphere.  This is where sensors come to mind, using the specified gas sensors it is easy to determine the leakage of gas. 

What is a gas sensor

There are different types of sensors according to the gas, these types of sensors are used to locate and classify various gases. They are frequently employed to estimate gas concentrations and identify explosive or dangerous gases. In other words, a series of sensors known as MQ gas sensors (mq sensor) are used to determine a variety of gases, including alcohol, smoke, methane, LPG, hydrogen, NH3, benzene, and propane. These sensors consist of an electrode that has a sensing substance placed on top and is heated to increase its reactivity and sensitivity. When the type of gas is in the range, these electrodes determine by decreasing the resistance.

MQ series of the Gas Sensors

The gas sensors are divided into different series depending on the gas or application. These are

Series of Gas

Purpose/Type of gasses

MQ - 2

Methane, Butane, LPG, smoke

MQ - 3

Alcohol, Ethanol, smoke

MQ - 4

Methane, CNG Gas

MQ - 5

Natural gas, LPG

MQ - 6

LPG, butane gas

MQ - 7

Carbon Monoxide

MQ - 8

Hydrogen Gas

MQ - 9

Carbon Monoxide, flammable gasses

MQ - 131


MQ - 135

Air Quality (CO, Ammonia, Benzene, Alcohol, smoke)

MQ - 136

Hydrogen Sulfide gas

MQ - 137


MQ - 138

Benzene, Toluene, Alcohol, Acetone, Propane, Formaldehyde gas, Hydrogen

MQ - 214

Methane, Natural gas

What is 1ppm equal?

The quantity of gas by volume in the air is referred to as concentration when measuring gases like carbon dioxide, oxygen, or methane. 1 ppm can stand in a variety of ways depending on the chemical being tested. The preferred units for expressing ppm are milligrams per kilograms (mg/kg), microliters per liter (L/L), and micrograms per litre (g/L). a better illustration

The ratio of specified gas to another gas is expressed in the parts-per-million (abbreviated as ppm).  For instance, If you are considered to measure methane at 1 parts-per-million, one molecule would be methane other molecules would be some other gas present in the atmosphere.

ppm = 1/10,00,000 = 0.0001%


Short description and features of each gas sensor

MQ - 2 Sensor Module 

The MQ2 Gas Sensor module is excellent for detecting gas leaks (home and industry). The H2, LPG, CH4, CO, alcohol, smoke, or propane can all be detected using this device. Its great sensitivity and quick response time allow for the earliest measurement feasible. The potentiometer allows the sensor's sensitivity to be changed. Depending on the amount of smoke or gas present in the air, the sensor's voltage output varies. The sensor produces a voltage that is proportionate to how much smoke or gas is present.

MQ - 2 Sensor Module

MQ - 3 Sensor Module

The MQ3 Gas Sensor module is excellent for detecting gas leaks (in home and industry). It is capable of detecting CO, CH4, Benzine, Hexane, LPG, and Alcohol. Measurements may be made as soon as feasible due to their high sensitivity and quick reaction rate. The potentiometer can be used to modify the sensor's sensitivity. This low-cost semiconductor gas sensor module is very simple to operate and has both analog and digital output. This Gas Sensor module can be used in breathalyzers because it is sensitive to alcohol. Benzine is similarly only weakly sensitive to MQ3 Sensor.

MQ - 3 Sensor Module

MQ - 4 Sensor Module(Methane, CNG Gas)

MQ - 4 sensor module

The MQ-4 Gas Sensor is a quick and dependable natural gas sensor with good sensitivity to propane and butane as well as high sensitivity to natural gas and methane. This low-cost, long-lasting natural gas sensor is frequently used to find gas leaks.

MQ - 5 Sensor Module(Natural Gas and LPG)

MQ-5 Gas Sensor Detectors are highly sensitive and react quickly. The output of the sensor is an analog resistance. Simply provide the heating coil with 5V, add a load resistance, and connect the output to an ADC.

MQ - 6 Sensor Module (LPG, butane gas)

The MQ-6 Sensor is an easy-to-use liquefied petroleum gas (LPG) sensor that can detect airborne LPG concentrations (which are primarily made of propane and butane). The MQ-6 is capable of detecting gas concentrations between 200 and 10,000 ppm. This sensor responds quickly and with excellent sensitivity. The output of the sensor is an analogue resistance. Simply provide the heating coil with 5V, add a load resistance, and connect the output to an ADC.

MQ - 6 Sensor module

MQ - 7 Sensor Module (Carbon Monoxide)

This type of series module is used to determine the CO, which is clean air and has a lower conductivity. It uses a cycle of high and low temperatures to make the detection and detects CO when the temperature is low (heated by 1.5V).

MQ - 7 Sensor module

MQ - 8 (Hydrogen gas(H2))

This module is suitable for determining Hydrogen Gas and can be used to measure concentrations between 100 and 10,000 ppm. Heater drive and measurement circuit implementation are simple. This sensor is built for durability and consistent output. 

MQ - 9 (Carbon Monoxide, flammable gasses)

This module is suitable for determining CO and flammable gases which in clean air have a lower conductivity. When the temperature is low, it detects CO by cycling between high and low temperatures (heated by 1.5V). Both the sensor's conductivity and the gas concentration are increasing. It identifies methane, propane, flammable gases, etc. when the temperature rises (heated by 5.0V) and cleans the other gases as it is adsorbed under low temperature.

MQ - 9 gas sensor

MQ - 131 (Ozone)

The MQ131 gas sensor is a sensitive component and it has a reduced conductivity in clean air. when there is ozone gas. Both the sensor's conductivity and the gas concentration are increasing. Please use a basic electrical circuit to convert the change in conductivity to a signal that corresponds to the amount of gas present.

MQ-131 gas sensor

MQ - 135, Air Quality (CO, Ammonia, Benzene, Alcohol, smoke):

The MQ-135 Gas Sensor can identify dangerous gases and smoke, including ammonia (NH3), sulphur (S), benzene (C6H6), and CO2. This sensor, like the others in the MQ series of gas sensors, has a pin for both digital and analogue output. The digital pin turns high when the amount of these gases in the air exceeds a predetermined threshold. The onboard potentiometer can be used to adjust this threshold value. An analogue voltage that is produced by the analogue output pin can be used to approximatively determine the concentration of various gases in the atmosphere.

MQ - 135, Air Quality sensor

MQ - 136 (Hydrogen Sulfide Gas)

The MQ136 Gas Sensor can be used to keep track of hydrogen sulphide gas concentrations. The sensor's conductivity increases and the concentration of the target hydrogen sulphide gas rise when it is present. High sensitivity to hydrogen sulphide and low sensitivity to other flammable gases characterize the MQ136 gas sensor. It is inexpensive and appropriate for a variety of uses.

MQ - 137 (Ammonia)

The conductivity of the sensor increases along with the concentration of NH3 gas when it is present. A simple circuit can be used by users to translate changes in conductivity into the corresponding output signal of gas concentration. The MQ137 gas sensor is very sensitive to NH3 gas and has good monitoring capabilities for organic amines like trimethylamine and calamine. It is a type of inexpensive sensor for many purposes that can detect different gases, including ammonia. It has many advantages including a long lifespan, low cost, a straightforward drive circuit, and strong sensitivity to NH3 gas over a wide range.

MQ - 138 (Benzene, Toluene, Alcohol, Acetone, Propane, Formaldehyde gas, Hydrogen):

The conductivity of the sensor increases as the gas concentration does. Through a straightforward circuit, users can translate the change in conductivity to the corresponding output signal of gas concentration. Toluene, acetone, alcohol, and methanol are highly sensitive to the MQ138 gas sensor, which also performs well when monitoring hydrogen and other organic vapours. It is a type of inexpensive sensor for various applications and is capable of detecting different organic gases. It offers benefits including a long lifespan and low cost,  and it has good sensitivity to organic vapour gas over a wide range.

MQ - 214 (Methane and Natural Gas )

Methane (CH4) gas sensor MQ-214 displays its reading as an analogue voltage after detecting the levels of methane in the air.  These gas sensors can identify gases that, are in high concentrations. Detectable concentration: 500–10,000 parts per million for LPG and propane, 1000–20,000 for methane, and 500–10,000 for hydrogen.


There are several types of gas sensors and a wide variety of mq2 gas sensor applications. You can select the most appropriate one required for your application or project based on the description provided above.

Components and Supplies

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