MQ-135 Gas Sensor Explained Air Quality Detection Made Simple

How the MQ-135 Sensor Works

The MQ-135 sensor uses a tin dioxide (SnO₂) semiconductor as its sensing element. This material has a unique property: its electrical conductivity changes when it comes in contact with specific gases.

Key Components

• Sensing Element: SnO₂-coated ceramic
• Heater Coil: Maintains optimal temperature for gas detection
• Electrodes: Measure changes in resistance

Working Principle

1. Gas Interaction: When the sensor is exposed to gases like ammonia, carbon monoxide, or VOCs, chemical reactions occur on the surface of the SnO₂ semiconductor.
2. Resistance Change: These reactions alter the electrical resistance of the sensor.
3. Signal Conversion: The sensor converts this resistance change into an analog voltage signal.
4. Data Interpretation: Microcontrollers like mq135 gas sensor Arduino or Raspberry Pi can read this signal to determine gas concentration.

The higher the gas concentration, the more pronounced the change in resistance, making the mq 135 air quality sensor an effective tool for air quality assessment.

Calibration and Accuracy

Proper calibration is essential for reliable readings, ensuring the mq 135 sensor specifications reflects gas concentrations. Environmental factors like temperature and humidity can influence its performance.

• Exposing the sensor to a known gas concentration
• Adjusting output according to the mq 135 sensor working principle in the datasheet
• Repeating the process periodically to account for sensor drift

Tip: Always check the temperature and humidity conditions during calibration, as they affect sensor accuracy.

Applications of the MQ-135 Sensor

The mq 135 sensor uses are highly versatile and used across multiple domains. Here’s a breakdown of its primary applications:

1. Air Quality Monitoring

• Indoor Air Quality Monitors: Detect pollutants in homes, offices, and classrooms.
• Wearable Devices: Track exposure to harmful gases in urban areas.
• IoT Solutions: Integrate with smart devices for real-time air quality updates.

2. Industrial Safety

• Monitor hazardous gas levels in factories, chemical plants, and laboratories.
• Trigger alarms or ventilation systems when dangerous gas concentrations are detected.

3. Environmental Monitoring

• Track pollution levels in cities and rural areas.
• Support research studies and data collection for environmental impact assessments.

4. Smart Home Automation

• Control ventilation systems automatically based on air quality.
• Alert homeowners when indoor air quality falls below healthy levels.

5. DIY and Educational Projects

• Popular among students and hobbyists for learning microcontroller interfacing.
• Ideal for hands-on experiments in electronics and embedded systems.

6. Health Monitoring Devices

• Integrated into portable air quality monitors and smartwatches.
• Helps users avoid exposure to toxic gases in real time.

7. Automotive Air Quality Systems

• Monitor the cabin air of vehicles.
• Activate air purifiers or adjust ventilation when pollutants are detected.

8. Agricultural Applications

• Monitor greenhouse gases for optimal plant growth.
• Control ventilation systems to maintain ideal environmental conditions.

Limitations and Considerations

While effective, the co2 sensor mq135 may respond to multiple gases, affecting specificity. Temperature and humidity can impact readings, so compensation techniques are often needed.

Cross-Sensitivity

• The sensor may respond to multiple gases simultaneously.
• Interpretation of readings requires caution, especially in complex gas environments.

Temperature and Humidity Dependency

• High humidity or extreme temperatures can affect accuracy.
• Consider implementing compensation techniques in your circuits or software.

Limited Gas Specificity

• While versatile, the MQ-135 cannot distinguish between all gas types precisely.
• Use additional sensors if highly specific gas detection is required.

Tips for Using MQ-135 Effectively

Preheating the sensor and using filtering circuits improves accuracy. Pairing it with microcontrollers and averaging readings ensures reliable data for your projects.

• Preheat the Sensor: Give the sensor 24–48 hours of preheating before first use for stable readings.
• Use Filtering Circuits: Prevent electrical noise from affecting sensor output.
• Pair with Microcontrollers: Arduino, ESP32, or Raspberry Pi work well for real-time data collection.
• Implement Averaging: Take multiple readings to minimize fluctuations and improve accuracy.

  

Conclusion

The MQ-135 gas sensor is versatile, affordable, and beginner-friendly, essential for air quality monitoring, industrial safety, smart homes, and IoT projects. Understanding its mq 135 sensor range, calibration, and real-world applications lets you easily integrate it into your projects to create safer, healthier environments. More than a sensor, it’s a gateway into environmental electronics, IoT innovation, and modern smart technology solutions.