Supplementing Co2 help -

I am placing a 20lb Co2 tank w/ regulator into a smaller (6x10x4' tall) room. The room is constantly at 80 degrees w/ 45% RH. There are no vents so I need to inject CO2. I am hoping to avoid buying a CO2/PPM meter but do not want put to much into the air.

Does anyone have a good schedule for the regulator timer, or know a good, cheap meter?

you need to work out the math on how much you need to release over however long of time you want it to run...
you can run it for an hour on pumping it out slowly.. or run it 15min pumping it out fast and all in between.

Any idea where I can find the equation?

google around. How much co2 to use in grow room / co2 and timers / using co2 tank with timer