The MQ-2 Sensor is a low-cost semiconductor gas sensor for detecting combustible gases and smoke. It is widely used in hobby electronics, Arduino projects, ESP32 projects, gas-leak alarm prototypes, air-quality experiments, and portable gas-detection projects.
The sensor element uses tin dioxide (SnO2) as the gas-sensitive material. In clean air, the sensor has relatively low conductivity. When combustible gases are present, the sensor conductivity increases with gas concentration. With a simple external circuit, this change can be converted into an analog voltage signal that can be read by a microcontroller or comparator circuit.
The MQ-2 is especially sensitive to propane and smoke, and can also respond to natural gas and other combustible vapours. Because it reacts to several gases, it is best used as a general combustible-gas and smoke sensor rather than a selective gas analyser.
Download MQ-2 Sensor Datasheet (PDF)
| Sensor type | Semiconductor gas sensor |
| Gas-sensitive material | Tin dioxide, SnO2 |
| Primary detection targets | Combustible gases and smoke |
| Typical detectable concentration range | 300-10000ppm combustible gas |
| High sensitivity gases | Propane and smoke |
| Also suitable for | Natural gas and other combustible vapours |
| Heater voltage | 5.0V ±0.1V AC or DC |
| Test circuit voltage | 5.0V ±0.1V DC typical, maximum circuit voltage 24V DC |
| Heater resistance | 29Ω ±3Ω at room temperature |
| Heater power consumption | Up to 950mW |
| Load resistor | Adjustable, commonly selected to suit the measuring circuit |
| Standard test conditions | 20°C ±2°C, 55% ±5%RH |
| Recommended initial preheat time | At least 48 hours for stable measurements |
| Expected sensor life | Up to 10 years under suitable operating conditions |
Typical applications:
- Arduino, ESP32, Raspberry Pi, and other microcontroller gas-sensing projects
- Combustible gas leak detector prototypes
- Smoke detection experiments
- Portable gas detector projects
- Educational electronics and sensor demonstrations
- DIY alarm and monitoring systems
Helpful information:
- The MQ-2 is not a digital sensor. The sensing element changes resistance depending on gas concentration.
- A load resistor is required to convert the sensor resistance change into a measurable voltage.
- The heater draws significant current. Make sure your 5V supply can provide enough power.
- The sensor needs warm-up time. Readings directly after power-up may drift and should not be treated as calibrated measurements.
- For repeatable measurements, allow the sensor to stabilize before taking readings.
- Temperature, humidity, oxygen concentration, airflow, and sensor age can affect readings.
- The MQ-2 responds to several gases, so it cannot reliably identify one specific gas without additional filtering or calibration.
| Pin information | The MQ-2 sensing element has 6 pins. Pins 2 and 5 are used for the heater. Pins 1 and 3 are internally connected, and pins 4 and 6 are internally connected for the sensing electrodes. |
| Heater connection | Apply 5V ±0.1V to the heater pins. |
| Sensing connection | Use the sensing electrodes together with a load resistor to create an analog voltage output. |
| Important note | Do not apply the heater voltage to the sensing electrode pins. Incorrect wiring can damage the sensor. |
Important safety note:
This sensor is intended for electronics projects, prototyping, education, and experimental gas detection. It is not a ready-made certified safety alarm. For life-safety, industrial safety, or code-required gas alarm installations, use properly certified gas detection equipment.
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