In part because I can’t help myself (and in part because I wanted something better than what’s already out there), I’m building my own smart home air quality sensors. The goal is a compact, silent, USB‑C powered Zigbee device that stays offline—because yes, my cardinal sin is Wi‑Fi smart devices. In this video I break down the board, the sensor choices, and why I’m prioritising Zigbee for a clean, local-only setup. The core of the build is the Sensirion STCC4 CO2 sensor paired with an SHT4X temperature/humidity sensor, giving me CO2 + temp + humidity in one go. It’s tiny, updates quickly (I’m running 30-second intervals), and it’s accurate enough for home use—plus it’s genuinely useful for knowing when to open a window, especially once you get into that “I feel it” range above ~1000 ppm. I’m also adding an optional Bosch BMV080 particulate sensor (PM1/PM2.5/PM10) that somehow manages fanless laser-based readings, and I’m planning a Bosch BME690 VOC sensor too—though Zigbee support for some of these data types is currently a pain, so I’m writing custom bits. The ESP32‑C6 gives me Zigbee and Wi‑Fi as an option, but you already know which one I prefer.