# MQ-135 Air Quality Sensor

Day 32 of the 100 Days 100 IoT Projects collection. Board: ESP32.

The MQ-135 sniffs the air for harmful gases on the ESP32 and reports quality levels. Your own indoor air watchdog.

## How it works

The MQ-135 reacts to several airborne contaminants, and the ESP32 converts its analog output into air-quality bands from fresh to poor. Because the sensor responds to multiple gases, calibration against clean air gives you a meaningful baseline to judge readings by.

## What you'll learn

- Air quality indexing
- Multi-gas sensitivity
- Baseline calibration
- Analog band classification

Full project (code, wiring diagram, Wokwi simulation): https://github.com/kritishmohapatra/100_Days_100_IoT_Projects/tree/main/MQ_135_Gas_Sensor_with_ESP32_(MicroPython)

Summary by SkillShop. Code and diagrams belong to the original repo.