MQ-135 Air Quality & Hazardous Gas Sensor Module (Environmental Monitor Board)
Take complete control over your indoor environment and pollution tracking systems with the industrial-grade MQ-135 Air Quality Sensor Module. Engineered for comprehensive atmospheric monitoring, this high-sensitivity module utilizes an advanced tin dioxide semiconductor layer that acts as an excellent all-in-one monitor against airborne contaminants, toxic smoke, and hazardous gases.
The MQ-135 sensor is heavily optimized to detect ammonia, benzene, alcohol, steam, carbon dioxide, and airborne smoke particles with exceptional speed. It serves as an essential diagnostic node for smart air purifiers, industrial ventilation control loops, smart home weather stations, and DIY pollution monitoring rigs.
Key Features
Broad-Spectrum Pollution Tracking: Highly responsive to a wide array of harmful gases and organic vapors, making it the definitive hardware choice for calculating general air quality indexes.
Dual Output Architecture: Built with both a Digital Output for instantaneous high/low safety alarm triggers and an Analog Output for real-time parts-per-million concentration mapping.
Adjustable Alarm Threshold: Features an onboard multi-turn potentiometer, allowing you to finely adjust the digital trigger point to match your specific clean-air background baseline.
Onboard Voltage Comparator: Assembled with a highly stable comparator integrated circuit, ensuring clean, sharp digital square waves that eliminate false triggers.
Explosion-Proof Stainless Steel Mesh: Designed with a dual-layer stainless steel mesh cover that protects the internal heated filament while keeping safe airflow moving into the sensor chamber.
Real-Time LED Status Monitoring: Equipped with two independent indicators—one for central power tracking and another that lights up instantly when pollution levels pass your preset safety limit.
Technical Specifications
Feature | Specification |
Sensor Type | Semiconductor Gas Sensor (MQ-135) |
Target Hazards | Ammonia, Benzene, Alcohol, Steam, Carbon Dioxide, Smoke |
Operating Voltage | 5V DC Nominal |
Operating Current | Approx. 150 mA |
Detection Concentration Range | 10 to 1000 ppm (Parts-Per-Million) |
Output Type | Dual Output: Analog Output + Digital Output |
Active Logic State | Digital Output drops LOW (0V) when safety thresholds are crossed |
Mounting Layout | Pre-drilled screw holes for secure panel or wall attachment |
Board Dimensions | 32 mm x 20 mm x 22 mm |
Hardware Wiring & Pin Mapping
The module breaks out a 4-pin interface that maps directly to standard microcontrollers like Arduino, ESP32, STM32, and Raspberry Pi:
VCC: Connects to a stable +5V DC power supply rail. (Requires a dedicated 5V source to correctly power the internal heating element).
GND: System Ground Reference.
DO (Digital Output): Outputs a stable High/Low logic level. Connect this straight to a digital input or hardware interrupt pin. It stays HIGH in standard conditions and drops LOW when pollution or gas leakages cross your threshold.
AO (Analog Output): Outputs a varying voltage signal corresponding directly to the concentration of contaminants in the air. Connect this to an analog pin to process exact parts-per-million calculations and air quality index algorithms.
Common Applications
Smart Air Purifier Systems: Integrate with ventilation relays to automatically kick-start fresh air intake fans or HVAC air scrubbers whenever carbon dioxide or smoke values spike inside a room.
Smart Home Weather Stations: Build custom indoor air quality monitors that report local environmental health scores straight to an LCD screen or cloud dashboard.
Industrial Workshop Safety Panels: Deploy near chemical storage lockers or painting booths to track accumulating organic solvent vapors.
Academic Automation Projects: An excellent, entry-level diagnostic module for university robotics labs, green-energy networks, and student engineering workshops focusing on environmental science.
💡 Operating Tip: The MQ-135 sensor requires a "Preheat / Burn-in" period before it can output accurate readings. After powering the module on for the very first time, let it sit powered up for 24 to 48 hours to balance the internal chemical sensing element. For subsequent uses, allow 1 to 2 minutes of warm-up time until the heater stabilizes. The module will become warm to the touch during normal operation—this is perfectly normal behavior for the internal heater loop.
Package Includes:
1 x MQ-135 Air Quality Gas Sensor Module