Well we used all of the math to try and get the CO2 right, bought the testing kit (was $34 + $5 per test) and thought we were pretty ontrack. I am an electrician and of course looking for ways to automate as much as possible. Went on Ebay, found a seller that was selling CO2 sensor/control for $230.00 BEST money we spent. Wish we would have saved the original $84 we spent on the syringe test kit!! The sensor is SIMPLE, and FAST and ACCURATE!! We have our room sealed very well, and are amazed that 15 minutes or so of a person in the room will raise the CO2 level by about 300 PPM. Our CO2 comsumption has gone down, and we now have a consistant level. The sensor I found even has software available so I can monitor the CO2 level OUTSIDE of the room!
So all in all, my opinion is, if you really want to use CO2, think seriously about looking for an electronic control as well. BTW, dont waste your money on the controls that claim to have FUZZY logic for the level. Our CO2 level never varies more or less than 50 PPM and it is a standard control. The fuzzy logic controls I have seen START at almost $500 and go up as high as you want to spend.
Again... just MHO