Description

MQ-9 Carbon Monoxide & Combustible Gas Sensor Module

Product Description

The MQ-9 Carbon Monoxide (CO) & Combustible Gas Sensor Module is a versatile and highly sensitive gas detection solution designed for monitoring carbon monoxide and flammable gases such as methane, LPG, and propane. This sensor module is widely used in gas alarm systems, safety monitoring devices, industrial control systems, and embedded electronics projects, making it an essential component for both professional and educational applications.

Carbon monoxide is a toxic, colorless, and odorless gas produced by incomplete combustion in engines, heaters, stoves, and industrial processes. Even low concentrations of CO can pose serious health risks, while higher concentrations can be fatal. In addition to CO, combustible gases such as methane and LPG present explosion and fire hazards when leaked. The MQ-9 sensor module enables early detection of these gases, helping to improve safety and prevent accidents.

The MQ-9 sensor operates using semiconductor gas sensing technology based on a sensitive tin dioxide (SnO₂) layer. When exposed to target gases, the sensor’s electrical resistance changes proportionally to gas concentration. These resistance changes are converted into electrical output signals that can be easily processed by microcontrollers or alarm circuits. This sensing principle is widely used in gas detection and is explained in detail in general gas sensor documentation:
👉 https://en.wikipedia.org/wiki/Gas_sensor

One of the defining features of the MQ-9 module is its dual-mode detection capability. The sensor is optimized to detect carbon monoxide at lower temperatures and combustible gases at higher temperatures by controlling the internal heater element. This makes the MQ-9 particularly useful in applications where both toxic and flammable gas monitoring is required using a single sensor.

The MQ-9 module typically provides both analog and digital outputs. The analog output delivers a continuous voltage signal proportional to gas concentration, making it suitable for real-time monitoring, data logging, and calibration. The digital output is generated through an onboard comparator and produces a HIGH or LOW signal when gas concentration exceeds a user-defined threshold, making it ideal for triggering alarms, relays, or automatic safety responses.

An onboard potentiometer allows users to adjust the sensitivity and detection threshold of the digital output. This flexibility enables the MQ-9 to be adapted to different environments, whether it is a residential gas alarm, an industrial monitoring system, or a laboratory experiment.

The MQ-9 sensor module operates on a standard 5V DC power supply, allowing easy integration with popular development platforms such as Arduino, ESP8266, ESP32, and other microcontroller-based systems. Its simple interface and widespread use make it a common choice in electronics education and prototyping. General information on interfacing sensors with microcontrollers can be found here:
👉 https://www.arduino.cc/en/Tutorial/Foundations/Sensors

Like other semiconductor gas sensors, the MQ-9 requires a preheating (warm-up) period to stabilize the sensing element before accurate readings can be obtained. Once warmed up and calibrated, the sensor provides stable and repeatable results suitable for continuous monitoring.

Thanks to its low cost, wide detection range, and dual gas capability, the MQ-9 Carbon Monoxide & Combustible Gas Sensor Module is widely used in home safety alarms, industrial gas detectors, automotive exhaust monitoring, and IoT-based safety systems. It offers an effective balance between performance, flexibility, and affordability.

---

Key Features & Benefits

Dual Gas Detection Capability

• Detects carbon monoxide (CO)

• Detects combustible gases such as LPG, methane, and propane

• Ideal for multi-gas safety applications

Analog & Digital Output

• Analog output for continuous gas concentration monitoring

• Digital output for threshold-based alarms and control

• Supports simple and advanced system designs

Adjustable Sensitivity

• Onboard potentiometer for setting alarm thresholds

• Customizable detection levels

• Helps reduce false alarms

Semiconductor SnO₂ Sensor Technology

• Proven and widely used gas sensing principle

• Reliable performance after warm-up

• Long operational lifespan

Fast Response Time

• Quickly detects gas concentration changes

• Suitable for real-time safety monitoring

• Enhances early warning capability

Microcontroller Friendly

• Operates on standard 5V DC

• Compatible with Arduino, ESP, and other platforms

• Simple wiring and signal processing

Compact & Modular Design

• Small footprint for easy installation

• Suitable for embedded systems and enclosures

• Lightweight and portable

Cost-Effective Safety Solution

• Affordable alternative to industrial sensors

• Ideal for prototypes, education, and small-scale deployments

• Widely used in DIY and IoT projects

---

Applications

• Carbon monoxide gas alarms

• Combustible gas leak detection

• Home and commercial safety systems

• Industrial gas monitoring

• Automotive exhaust monitoring

• Smart home and IoT safety devices

• Embedded systems and electronics education

---

Why Choose the MQ-9 Gas Sensor Module?

The MQ-9 Carbon Monoxide & Combustible Gas Sensor Module offers a practical and flexible solution for detecting both toxic and flammable gases using a single sensor. Its dual-output design, adjustable sensitivity, and compatibility with common microcontrollers make it suitable for a wide range of safety, monitoring, and development applications. With proper calibration, the MQ-9 provides reliable gas detection at a cost that makes it accessible for both professionals and learners.

Data sheet