Adafruit SCD-40 - True CO2, Temperature and Humidity Sensor (STEMMA QT / Qwiic)Take a deep breath in now slowly breathe out. Mmm isn't it wonderful? All that air around us, which we bring into our lungs, extracts oxygen from and then breathes out carbon dioxide. CO2 is essential for life on this planet we call Earth we and plants take turns using and emitting CO2 in an elegant symbiosis. But it's important to keep that CO2 balanced you don't want too much around, not good for humans and not good for our planet. The SCD 40 is a