MQ9 CO Flammable Gas Sensor Module


MQ9 gas sensor belongs to the MQ sensor family series designated for the detection and identification of flammable and combustible gases. The module can detect flammable and carbon monoxide gas in the range of 10 – 10000ppm. Its most common application is in the field of domestic gas leakage alarms and detectors with a high sensitivity to propane and smoke.

The sensing material of the MQ9 gas sensor is SnO2, which with lower conductivity in clean air. It makes detection by method of cycle high and low temperature and detects CO when low temperature (heated by 1.5V). The sensor’s conductivity is higher along with the gas concentration rising. When the high temperature (heated by 5.0V), it detects Methane, Propane, etc. combustible gas, and cleans the other gases adsorbed under low temperature. Please use a simple electro circuit, to convert the change of conductivity to the corresponding output signal of gas concentration. MQ9 gas sensors must always be avoided to be used in an environment where either a highly corrosive gas or organic silicon steam has been permutated as it interferes and can potentially destroy the sensing element of the MQ9 sensing module.

MQ9 CO Flammable Gas Sensor Module-Pinout

MQ9 Gas Sensor Key Features

  • High sensitivity to Methane, Propane, and CO
  • Long life and low cost
  • ESD Protection
  • Overvoltage Protection
  • Early warning triggers for harmful fumes
  • Fast response time
  • Simple drive circuit

MQ9 Gas Sensor Pinout

MQ9 CO Flammable Gas Sensor Module Pinout
Pin NamePin No.Description
VCC1This pin powers the module, typically the operating voltage is +5V
GND2Used to connect the module to the system ground
DO3You can also use this sensor to get digital output from this pin, by setting a threshold value using the potentiometer
AO4This pin outputs 0-5V analog voltage based on the intensity of the gas.

MQ9 Specifications

  • Detection Gas: Carbon Monoxide and Flammable Gas
  • Concentration: 10-10000ppm CO, 100-10000ppm Combustible Gas
  • Supply Voltage: <10V
  • Heater Voltage: 5.0V ± 0.2V (High), 1.5V ± 0.1V (Low)
  • Load Resistance: Adjustable
  • Heater Resistance: 31Ω ± 3Ω
  • Standard Encapsulation: Bakelite
  • Loop Voltage Vc: ≤10V DC
  • Heater Voltage VH: 5.0V±0.2V AC or DC (High)/ 1.5V±0.1V AC or DC (Low)
  • Sensing Resistance Rs: 2KΩ-20KΩ(in 100ppm CO )
  • Heater Consumption: <350mW


  • Domestic gas leakage detector
  • Industrial gas detector
  • Portable gas detector


You can download the datasheet for MQ9 CO/Flammable Gas Sensor Module by clicking the link given below:

See Also: CD4059 Program Divide-by-N Counter | ADXL335 Accelerometer Sensor Module | FC-28 Soil Moisture Sensor Module