My name is Jason and I work in product development at CO2meter.com. I try to keep up with forums for arduino and other similar products to provide guidance to projects that involve air quality control. We have clients that run large scale mushroom growing operations, and along with Temperature and humidity, it is also important to monitor CO2 levels. This article explains a little about why: http://www.co2meter.com/collections/mushrooms-co2
It lists a few products that we often provide for our clients, but to incorporate into an automated system I would look into the Cozir RH/T http://www.co2meter.com/collections/co2-sensors/products/cozir-0-2-co2-sensor
. This provides real time CO2 level, Temperature, and humidity over UART. I have written some basic libraries to work with MCUs and getting it running on an arduino is very straightfoward.
If you have any questions or would like the code for running these please let me know.