Room in a room here... When someone knowledgable replies for Dirthawker--is there any a/c unit that will act like a dehumidifier as well? Maybe hit two birds with one stone... and I'm confused how a window a/c unit doesn't exhaust the CO2? Or wait.. guess it sucks air from the outside in.. so that should be fine.. except for any exhaust vents in the room?
I'm not an AC pro - but I know a bit about AC's and can answer your questions. All AC units act as dehumidifiers. Some actually have a setting that just dehumidifies - you can often find this feature in the spec sheets. The water for window mount AC units usually drains outside - you've likely seen a puddle under one... that is the dehumidification in action! On a side note - the runoff from your AC (or dehumidifier) is usually close to 0 PPM water! Add it to your res - feed it to your plants again!....and again...and--you get the idea!
Window units recirculate the air in the room. They do not exhaust your room air out the back. Without modification, the water from the dehumidification will drain out the back. Folks have been busted by this water! It actually smells of weed and can easily be detected by dogs and law.
So this is good news - Your AC will actually help you circulate your CO2 in the room! Get the Sentinel CHHC-1, or similar product to coordinate your exhaust with your CO2... so you dont exhaust your precious CO2.
On the note of CO2 - with tanks you don't have to worry as you do not have a burner that needs oxygen. But, if you do use a CO2 gen with a burner, you will need to exchange the air in your room more often to properly combust the gas and max what the burner can generate. With tanks, Stink is able to seal his room without having to exchange air that often. With a CO2 generator you need to be sure there is enough oxygen in the air so that your burners burn a nice blue color rather than yellow. 2 reasons: If the gas does not combust completely it leaves carbon monoxide - deadly gas! Secondly, if you do not combust completely your burners will have to fire up more often because they are not efficiently producing CO2. This then raises the temps in your grow room as your burners try to maintain your PPMs.
I learned this by reading my Hydrogen manual. And then applied this info to a zone that was running hot as hell - working the large AC unit overtime! It was sealed and we were not allowing enough oxygen in to completely combust and our CO2 gen was working overtime... Our flames were more yellow. We started exchanging the air once every couple hours and the CO2 gen immediately started working more efficiently - burning half the time to maintain 1200 PPM.