This repository contains good resources to getting started with IoT. Here various sensor is used to connect with Arduino Uno and ESP32 and their program is available.

Interfacing Sensors With Arduino

Real-time ammonia gas monitoring system using ESP32, MQ gas sensor, and DHT22. Streams live NH3, temperature, and humidity data to an Android app over BLE. Triggers SMS alerts via GSM900a when levels exceed a configurable threshold.

Air-Q nose is an attempt to build a air quality sensor with 8 different MQ sensor and fuse the data into one model for each gas