I wasn't satisfied with #Sensirion's #USB powered #CO2 traffic light due to its hardcoded thresholds, so I built my own using a #RaspberryPiZero with solderless #ZeroDongle, #I2C #BreakoutGarden Mini #pHAT, Sensirion #SCD41 CO₂ sensor breakout and the #Pimoroni #LEDShim. All parts available at https://shop.pimoroni.com except for the Pi which is sold out.

The code behind it is based on two library examples by @gadgetoid and available at https://github.com/xtaran/co2-led-meter under the #MITLicense.