MQ 9 Gas Sensor Module Carbon Monoxide and Flammable

AED 19.95



The MQ9 sensor module is a highly responsive and versatile gas sensor capable of and features power and output LEDs, Additionally, it incorporates a potentiometer that enables the adjustment of sensitivity according to specific gas concentration requirements, The MQ9 sensor module provides two output options digital and analog. This allows for flexibility in connecting the sensor to different systems and interfaces, facilitating seamless integration into various applications.


Package Includes:

  • 1x MQ9 CO and flamable Gases Sensor



  • Fast Response Time: The module offers a rapid response time, ensuring quick detection and timely alerts in the presence of flammable gases or carbon monoxide.
  • Easy Positioning: It includes four screw holes, facilitating easy and secure positioning of the sensor module in different installations or devices.
  • Simple Drive Circuit: The module features a straightforward drive circuit, simplifying its integration into different systems or projects.
  • Suitable for Home and Factory Gas Monitoring: The MQ9 sensor module is specifically suitable for gas leakage monitoring in both home and factory environments. It can effectively detect carbon monoxide and other flammable gases, ensuring safety and enabling prompt actions.
  • High-Quality Dual-Panel Design: The module boasts a high-quality dual-panel design, offering enhanced durability and reliability. It includes a power indicator and TTL signal output for easy monitoring and integration.
  • TTL Output Valid Signal: The TTL output signal of the module is valid when it is low. This allows direct connection to microcontrollers or relay modules, simplifying the interface setup.
  • Analog Output Voltage: The analog output voltage of the module varies proportionally with the gas concentration. As the concentration increases, the voltage output also increases, providing a continuous measurement signal.
  • Improved Sensitivity for Carbon Monoxide Detection: The MQ9 sensor module exhibits enhanced sensitivity specifically for detecting carbon monoxide, ensuring accurate and reliable monitoring.
  • Dual Functionality: The module can be used as both a digital and analog sensor, offering flexibility based on the requirements of the application.
  • Adjustable Sensitivity: The sensitivity of the digital pin can be easily adjusted using the potentiometer, allowing fine-tuning of the sensor module's response to specific gas concentrations.



The MQ9 sensor module is an advanced and highly efficient gas sensor that offers exceptional responsiveness and versatility. It is specifically designed to detect a wide range of flammable gases and carbon monoxide with remarkable precision. Its sensitivity range is extensive, spanning from 100 parts per million (ppm) to 10,000 ppm for combustible gases and 10 ppm to 1000 ppm for carbon monoxide, enabling accurate gas detection across various concentration levels. One of the standout features of the MQ9 sensor module is its rapid response time, facilitated by an internal heater that activates as soon as a 5V power supply is provided. This heater ensures the sensor reaches its optimal operating temperature quickly, enabling swift and reliable gas detection. The module incorporates power and output Light Emitting Diodes (LEDs) that offer convenient visual indicators to monitor its operational status, allowing users to easily determine if the sensor is functioning correctly. the MQ9 sensor module includes a potentiometer, which grants users the ability to fine-tune the sensitivity according to specific gas concentration requirements. This adjustable sensitivity enhances the sensor's adaptability to diverse environments and ensures accurate readings tailored to the application at hand. the MQ9 sensor module provides two output options: digital and analog. This dual output capability confers significant flexibility in integrating the sensor into various systems and interfaces. The digital output typically generates a signal that transitions from low to high when the gas concentration surpasses a pre-set threshold, enabling easy integration with digital circuits or microcontrollers. Simultaneously, the analog output delivers a continuous voltage signal that is proportionate to the detected gas concentration, allowing for seamless integration into systems that necessitate analog input.


Principle of Work:

The MQ9 sensor module simplifies gas detection processes, offering flexibility in choosing between the analog pin or digital pin for gas sensing. Before utilizing the sensors, it is essential to pre-heat them for a certain period. Once the gas comes into contact with the sensor, the potentiometer needs to be adjusted until the output LED and digital pin both indicate a high state. When the sensor is exposed to a specific concentration of gas, the digital pin will transition to a high state (5V), indicating the presence of the gas. Conversely, if the gas concentration is below the threshold, the digital pin will remain in a low state. Similarly, the analog pin can be employed to achieve the same outcome. By reading the analog values (ranging from 0 to 5V) using a microcontroller (MCU), it is possible to obtain a direct proportional measurement of the gas concentration detected by the sensor. To understand the sensor's response to different gas concentrations, you can experiment with these settings and adjust your program accordingly. It is crucial to calibrate the module before using it. The gas concentration is calculated by the sensor based on the resistance ratio, which involves the values of Rs (sensor resistance in the presence of gas) and R0 (sensor resistance at 1000 ppm LPG concentration). After preheating the sensor in clean air, you can upload the provided code and allow approximately 15 minutes for R0 to stabilize at a fixed value. Calibrating the module and allowing the resistance ratio to reach a steady state ensures accurate gas concentration measurements. This calibration process helps establish a reference point for subsequent gas detection readings and enhances the reliability and precision of the MQ9 sensor module.


Pinout of the Sensor:

Pin No:

Pin Name:




This pin powers the module, typically the operating voltage is +5V



Used to connect the module to the system ground


Digital Out

You can also use this sensor to get digital output from this pin, by setting a threshold value using the potentiometer


Analog Out

This pin outputs 0-5V analog voltage based on the intensity of the gas 




  1. Industrial Safety Systems: The MQ9 sensor module is utilized in industrial environments to ensure the safety of workers by detecting and monitoring the presence of flammable gases and carbon monoxide. It helps prevent potential accidents and enables prompt action in case of gas leaks.
  2. Gas Leakage Detection: The module is commonly employed in gas leakage detection systems for residential and commercial buildings. It can detect leaks of flammable gases such as methane, propane, and butane, allowing for early detection and prevention of hazardous situations.
  3. Fire Detection: The MQ9 sensor module plays a vital role in fire detection systems by detecting the presence of flammable gases that can indicate the early stages of a fire. It enables quick response and timely activation of fire suppression systems.
  4. Environmental Monitoring: The module is used in environmental monitoring systems to assess air quality and detect the presence of harmful gases. It helps monitor pollution levels and supports initiatives for maintaining a healthy and safe environment.
  5. Home Automation: The MQ9 sensor module can be integrated into home automation systems to enhance safety and security. It enables the detection of gas leaks, including carbon monoxide, providing alerts and triggering actions such as activating ventilation systems or sending notifications to homeowners.
  6. Gas Detectors and Alarms: The module is utilized in standalone gas detectors and alarms, providing reliable and accurate gas detection capabilities. It ensures the safety of occupants in residential, commercial, and industrial settings by providing early warnings in the event of gas leaks.
  7. HVAC Systems: The MQ9 sensor module is incorporated into heating, ventilation, and air conditioning (HVAC) systems to monitor gas levels and ensure optimal indoor air quality. It helps maintain a safe and comfortable environment by detecting and controlling the presence of harmful gases.
  8. Laboratory Applications: The module is employed in laboratory settings for gas detection and monitoring purposes. It ensures the safety of laboratory personnel by detecting the presence of flammable or toxic gases that may be used or produced during experiments or chemical processes.



  1. Connect the GND pin of the MQ9 sensor to any of the GND pins on the Arduino board. This establishes the ground connection between the sensor and the board, ensuring a common reference point for electrical signals.

  2. Attach the VCC pin of the MQ9 sensor to the +5V power source pin on the Arduino board. This provides the necessary power supply to the sensor for its operation.

  3. Connect the A out pin of the MQ9 sensor to the Arduino board's Analog pin A0. This allows the Arduino board to read the analog output from the sensor, which provides information about the detected gas concentration.



This Module doesn't need any Library to function.


The next sample code provides real-time gas concentration monitoring using the MQ9 sensor and visual feedback through the LED, along with informative messages on the Serial monitor:

#define MQ9pin A0
float sensorValue; // variable to store sensor value
int ledPin = 13; // pin for the LED

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600); // sets the serial port to 9600
  Serial.println("MQ9 warming up!");
  delay(20000); // allow the MQ9 to warm up

void loop() {
  sensorValue = analogRead(MQ9pin); // read analog input from pin A0
  Serial.print("Sensor Value: ");

  if (sensorValue > 400) {
    digitalWrite(ledPin, HIGH);
    Serial.println("High gas concentration detected! LED turned on.");
  } else {
    digitalWrite(ledPin, LOW);
    Serial.println("Gas concentration within safe range. LED turned off.");

  delay(2000); // wait 2s for the next reading


  1. We define a constant MQ9pin and two variables: sensorValue to store the sensor reading and ledPin to specify the pin connected to the LED.
  2. In the setup() function, the ledPin is configured as an output pin using pinMode(). The Serial communication is initiated with Serial.begin(9600), setting the baud rate to 9600. The message "MQ9 warming up!" is printed on the Serial monitor. The program then pauses for 20,000 milliseconds (20 seconds) using delay() to allow the MQ9 sensor to warm up.
  3. The main functionality is implemented in the loop() function, which runs repeatedly.
  4. Inside the loop(), the analogRead() function reads the analog input from MQ9pin (A0) and stores the sensor value in the sensorValue variable.
  5. The current sensor value is printed on the Serial monitor using Serial.print() and Serial.println().
  6. An if statement is used to check if the sensor value exceeds 400, indicating a high gas concentration. If it does, the digitalWrite() function sets the ledPin to HIGH, turning on the LED. A corresponding message is printed on the Serial monitor to indicate the detection of a high gas concentration.
  7. If the sensor value is below or equal to 400, the else block is executed. The digitalWrite() function sets the ledPin to LOW, turning off the LED. A message is printed on the Serial monitor indicating that the gas concentration is within a safe range.
  8. the code pauses for 2,000 milliseconds (2 seconds) using delay() before starting the next iteration of the loop().


Technical Details:

  • Target Gas: CO + Flammable Gases
  • Detectable Concentration: 100-10000ppm CO
  • Operating voltage: 5V
  • Heating resistor: 31 Ω ± 3Ω
  • Current consumption of the heating element ≤ 180mA
  • heating resistor voltage 5V ± 0,1V / 1,5V ± 0,1V
  • Heating energy output max. 350mW
  • Accuracy ≥ 3%
  • Response time ≤ 1 sec.
  • Response time after switching on ≤ 30 seconds.
  • VCC Working Voltage 4.9 5 5.1 V
  • PH Heating consumption 0.5 - 340 mW
  • RL Load resistance adjustable
  • RH Heater resistance - 33Ω±5% - Ω
  • Rs Sensing Resistance 2 - 20000 Ω
  • CO/CH4/LPG Scope Detecting Concentration 200 - 1000/10000/
  • Dimensions: 32(L)*20(W)*22(H)



Datasheet of the MQ9



The MQ-7 sensor is the closest alternative to the MQ-9 sensor that can detect both carbon monoxide (CO) and flammable gases. While the MQ-9 sensor is specifically designed for CO and flammable gases, the MQ-7 sensor is primarily intended for detecting carbon monoxide but can also respond to flammable gases to some extent lets compare between the MQ-9 and MQ-7 sensor modules:

  1. Target Gases:

    • MQ-9: The MQ-9 sensor module is designed to detect carbon monoxide (CO) and flammable gases.
    • MQ-7: The MQ-7 sensor module primarily detects carbon monoxide (CO), but it can also respond to some extent to flammable gases.
  2. Sensitivity:

    • MQ-9: The MQ-9 sensor module has a high sensitivity to both CO and flammable gases, with a detection range of 100ppm to 10,000ppm for combustible gases.
    • MQ-7: The MQ-7 sensor module has a sensitivity range of 20ppm to 2000ppm for carbon monoxide (CO) detection.
  3. Specificity:

    • MQ-9: The MQ-9 sensor module is specifically designed for CO and flammable gases, providing reliable and accurate detection for these gases.
    • MQ-7: The MQ-7 sensor module is primarily intended for carbon monoxide (CO) detection but can also respond to flammable gases to some extent. However, its sensitivity to flammable gases may be lower compared to dedicated flammable gas sensors.
  4. Application:

    • MQ-9: The MQ-9 sensor module is suitable for applications that require the detection of CO and flammable gases, making it useful for gas leakage monitoring systems in homes, factories, and other environments.
    • MQ-7: The MQ-7 sensor module is commonly used for carbon monoxide (CO) detection in various applications such as gas leak detectors, gas alarms, and air quality monitoring systems.
  5. Performance:

    • MQ-9: The MQ-9 sensor module provides a fast response time and high sensitivity to CO and flammable gases, making it well-suited for prompt gas detection and monitoring.
    • MQ-7: The MQ-7 sensor module offers good sensitivity to carbon monoxide (CO) and provides a relatively quick response time, allowing for efficient CO detection and monitoring.