you don't want to mess with that crap. I think just setting a tank on a timer would be more cost effective than that. If you are thinking about doing co2, you plan to do it from here on out, right? so why fuck around and do it wrong first? You'd be better of waiting and saving your $$ and doing it right. In the mean time, keep plenty of fresh air moving through.

google this
C.A.P Air-3 and C.A.P. PPM-3=
one is the sniffer (monitor) and one the controller.