That sounds about right. It's either the plants using up the CO² or some leaking or a combo of the two. You mighty be happier with 1800 ppm then refill at 1500-ppm. Try to hold it for 6 hours then exchange the air in the room. It should only take a few min. Then start the CO² up again until the lights go off then exhaust the air one last time for the day.
Zandor Reviewed by Zandor on . CO2 /Temps/Humidity Question!!! Small Grow Room Split Veg/Flower (currently vegging in Flower side to start perpetual grow). BTW, CO2 is the bomb... clones have taken off and doubled in size in 4 days, and just keep growing!!! Situation: I'm running co2 off a Telair 8001 in veg side that is demanding a boost every 6 minutes, drawdown is about 1-1.5 ppm / second between 1600 to 1400 ppm. So I end up getting a demand off the Telair for CO2 to bring it back up. Seems dialed in. BUT temps are staying at about 78-79 with Rating: 5