MQ-135 Air Quality Gas Sensor Module | CO₂, NH₃, Smoke & VOC Detector for Arduino, ESP32 & Raspberry Pi

The MQ-135 Air Quality Sensor Module is a versatile gas detection sensor designed to monitor indoor air quality by detecting a wide range of gases, including ammonia (NH₃), nitrogen oxides (NOx), alcohol, benzene, smoke, carbon dioxide (CO₂), and other volatile organic compounds (VOCs).

The module provides both analog and digital outputs, making it easy to interface with Arduino, ESP32, ESP8266, Raspberry Pi (with ADC), STM32, and other microcontroller platforms. With an onboard LM393 comparator and adjustable sensitivity, it is ideal for air quality monitoring, smart home systems, environmental monitoring, and IoT projects.

Note: The MQ-135 is best suited for relative air quality monitoring. It is not a calibrated CO₂ meter and should not be used where precise CO₂ concentration measurements are required.

Features

• Detects multiple gases including NH₃, NOx, alcohol, benzene, smoke, CO₂, and VOCs
• Analog and digital output signals
• Adjustable sensitivity using onboard potentiometer
• Fast response and recovery time
• High sensitivity to air quality changes
• Onboard power and output indicator LEDs
• Compatible with Arduino, ESP32, ESP8266, Raspberry Pi (with ADC), STM32, and other microcontrollers
• Simple 4-pin interface

Specifications

Applications

• Indoor Air Quality Monitoring
• Smart Home Systems
• HVAC Monitoring
• Environmental Monitoring
• Air Pollution Detection
• IoT Projects
• Industrial Monitoring
• Educational Electronics
• DIY Electronics
• Robotics