ShillehTek MQ-135 air quality gas sensor module with metal mesh top

MQ-135 Air Quality Hazardous Gas Sensor Module for Arduino

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MQ-135 Air Quality gas sensor module for Arduino detects NH3, NOx, CO2 and VOCs to monitor indoor pollution; analog and digital outputs ideal for logging air quality or triggering ventilation.

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Overview

Product Overview

The MQ-135 Air Quality Hazardous Gas Sensor Module for Arduino uses a sensitive Tin Dioxide (SnO2) sensing layer that changes conductivity when exposed to polluted air, letting you monitor common indoor pollutants such as ammonia (NH3), nitrogen oxides (NOx), alcohol, benzene, smoke and CO2. The board provides both a linear analog output for logging concentration trends and a digital output driven by an onboard LM393 comparator for simple alarm thresholds, and it mounts on a standard 4‑pin header (VCC, GND, DO, AO) that fits breadboards and Arduino shields. It can be calibrated against clean‑air Ro values to estimate PPM and includes an active heater that needs an initial 24‑hour burn‑in to stabilize readings—practical for makers building monitors or ventilation controls.

Questions & answers

Frequently asked questions

Yes. It is designed for Arduino projects and exposes a simple analog output plus a digital comparator output, so an Arduino can read pollutant trends or monitor a threshold alarm using standard input pins.
The board uses a standard 4-pin header labeled VCC, GND, DO, and AO, making it suitable for breadboards and Arduino shields. ShillehTek modules are sold pre-soldered, so basic jumper-wire setup does not require header soldering.
It provides AO, a linear analog signal for logging gas concentration trends, and DO, a digital signal from the onboard LM393 comparator for threshold-based alarms. The connector also includes VCC and GND power pins.
Yes. It can monitor indoor air-quality trends involving ammonia, nitrogen oxides, alcohol, benzene, smoke, and CO2, making it practical for maker air monitors, data loggers, warning indicators, or ventilation-control experiments.
The sensor includes an active heater and needs an initial 24-hour burn-in before readings stabilize. For estimated PPM values, calibrate against a clean-air Ro reference rather than expecting accurate numbers immediately after power-up.

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What's included

Features & Specs

Gas detection types Detects common pollutants including NH3, NOx, alcohol, benzene, smoke and CO2.

Sensor technology Uses a Tin Dioxide (SnO2) sensing layer that changes conductivity in polluted air.

Analog and digital Provides a linear analog output for concentration logging and a digital output via LM393 for alarm triggers.

Heater burn-in required Requires a 24-hour initial burn-in to stabilize the internal heater and improve accuracy.

Calibration capable Can be calibrated against known clean-air Ro values for more precise PPM measurements.

Compact interface Ships with a standard 4-pin header (VCC, GND, DO, AO) for breadboard and shield mounting.

DIY application use Ideal for Arduino-based pollution monitors and automated ventilation control projects.

Reference

Documents

Full Product Manual ShillehTek MQ-135 Air Quality Hazardous Gas Sensor Module for Arduino | ShillehTek Product Manual In-depth setup guide with wiring, code examples, and troubleshooting.

Datasheet

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