This project originated from my own need of a simple enough CO2 sensor that anyone can interpret without reading small numbers on a finicky display - but without losing the ability to trigger automation and logging the data to home assistant 
Originally started this last year as a one-off prototype and distributed a couple of these to friends & family, while figuring out there are other people that want such a solution.
That said, we were already well equipped at LinkGear and have a fantastic production partner: Yaosheng. Not only does this allow us to manufacture top-notch hardware at smaller quantities for a reasonable price, it also makes sure that all the requirements by the sensor manufacturers are being paid attention to.
We decided to go with SCD41 from Sensirion for the CO2 sensor - Sensirion is a highly reputable company and the SCD41 measures actual CO2 contents. This is paired with a BME280 for Temperature, Humidity and Pressure.
As outputs, there is an LED ring with 8 addressable SK6812 available. With the stock firmware they will display red, green or red according to the current CO2 level. But you can simply take control by flashing your own esphome config. Endless possibilities! We also included a small buzzer that can be used to give audio feedback on when ventilation is necessary. Oh and you can re-flash it easily by simply connecting to the USB-C port!
And if you have a specific use-case… the device has a QWIC connector where many other esphome compatible sensors are available from other vendors!
Get yours over at CO2 Ampel for ESPHome - Multi-Sensor Board - LinkGear
These are NOT pre-orders! We have plenty in stock.
Any feedback highly welcome!
This device is part of the “Made for ESPHome” program. I also want to mention that this goes beyond a hobbyist project with full EMC testing carried out in a lab and CE documents available. Please note that at this time the device is not FCC-approved/certified.
Docs: https://docs.linkgear.net/books/lg-eca1/page/manual-safety
Flasher: https://flash.linkgear.net/
Stock config: LinkGearMisc/products/lg-eca at main · performeon/LinkGearMisc · GitHub