A while back, I stumbled across the AirGradient project – a DIY air quality sensor built on the ESP8266 platform – and thought it would be interesting to build one to track the air quality where I live. It kinda worked, but I never got all of the sensors working correctly – the CO2 sensor in particular never reported data using their software. Fortunately, ESPHome supports all the sensors (and even the display) that AirGradient recommended, so I was able to get full sensor coverage.