co2 and scrubber on timers?

i have a 4x3x7=84 ft (give or take) room. if i want my scrubber to turn off when co2 is on how long do i keep scrubber off for? what would you do? i was going to set the co2 timer to go on 2 times a hour for 15 min at a flow rate of 0.02 while the lights are on at night hours? would i also need to make sure my window a/c is off? or even a space heater? i cannot afford a controller at this time so i have to do it this way ? thanks for the help