The SCD40 from Sensirion is a high quality Photoacoustic based CO₂ sensor capable of detecting 0 to 40000ppm with the best accuracy over 400-2000ppm ±(40ppm+5%). In order to improve accuracy the SCD40 has integrated temperature and humidity sensing built-in. For additional accuracy the SCD40 also accepts ambient pressure readings!

We've written an Arduino library to make reading the CO₂, humidity, and temperature very easy. It can be downloaded through the Arduino Library manager: search for 'SparkFun SCD4x' or it can be found in the Documents tab above.

Note: The SCD40 has an automatic self-calibration routine. Sensirion recommends 7 days of continuous readings with at least 1 hour a day of 'fresh air' for self-calibration to complete.

• SCD40 Datasheet
• Schematic
• Eagle Files
• Arduino Library
• Hardware repo