Well I appreciate the efforts. But as I stated I don't know too much about programming. The link really is not helping me. That uses an SD card shield and I don't understand most of the code. That has temp/humidity and co2 combined. I would like to keep it simple only using the Co2 sensor and have it control a relay. Just like my temperature project. I just never used a co2 sensor and that why I am hoping someone can guide me through connecting everything and with the code.