MQ-135 Air Quality Gas Sensor Module
The MQ-135 Air Quality Gas Sensor Module is a popular and reliable sensor used to detect a wide range of harmful gases and pollutants in the air. It works effectively for both indoor and outdoor air quality monitoring. This module helps protect people by sensing gases like ammonia (NH3), carbon monoxide (CO), benzene, smoke, and other volatile organic compounds (VOCs). Thanks to its fast response and high sensitivity, it plays a vital role in industrial safety, environmental monitoring, and smart home systems. The sensor supports real-time detection, which allows systems to react quickly to changes in air quality.
How It Works
This sensor uses a semiconductor material called tin dioxide (SnO2). When harmful gases are present, the sensor’s resistance decreases. This change causes the sensor’s output voltage to increase, indicating higher gas levels. The module outputs an analog signal that microcontrollers like Arduino, ESP32, or Raspberry Pi can easily read and process. Additionally, the module includes a digital output pin. You can set a threshold on this pin to trigger alarms or ventilation systems when gas concentration passes a safe limit. The sensor has a built-in heater powered by 5V, which maintains the sensor’s temperature for accurate and stable detection. Before using, the sensor needs a warm-up time of about 20 seconds.
Key Features
Detects a variety of harmful gases including NH3, CO, benzene, smoke, and more.
Offers high sensitivity with quick response time, ensuring timely detection.
Operates on a 5V DC power supply compatible with most microcontrollers.
Provides both analog and digital outputs for flexible use in various applications.
Compact and lightweight design makes it easy to install in different environments.
Suitable for both indoor and outdoor air quality monitoring projects.
Specifications
| Parameter | Value |
|---|---|
| Operating Voltage | 5 V DC |
| Sensor Type | Semiconductor (SnO2) – |
| Detection Range | NH3, CO, smoke, benzene, and other VOCs |
| Output | Analog voltage and digital output |
| Heater Voltage | 5 V DC |
| Warm-up Time | About 20 seconds |
| Response Time | Less than 10 seconds |
| Operating Temperature | -10 °C to +50 °C |
| Dimensions | About 32 mm × 20 mm |
Pin Configuration
| Pin | Name | Description |
|---|---|---|
| 1 | VCC | Power input (5 V DC) |
| 2 | GND | Ground |
| 3 | AO | Analog output voltage |
| 4 | DO | Digital output (threshold) |
Applications
Real-time monitoring of indoor and outdoor air quality to keep environments safe.
Industrial pollution control and worker safety systems.
Automation in smart homes to improve air quality and health.
Environmental research and data collection for air quality studies.
Health and safety monitoring in workplaces and public spaces.
