My set up is in a sealed grow room. It's in a spare room of my house. I have a mini-split aircon unit which works quite well but I'm worried my plants aren't getting enough carbon dioxide because they're in a sealed room. I'm in and out of the room a lot during the day so there will be a fair amount of air exchange in the room for most of the day but is this suffice? Or should I think about implementing some additional CO2?

We are moving to a new house soon and I won't have a mini-split aircon unit in the room. I could easily get one installed, but in the country where I live growing indoors is a bit of a grey area and I don't want people to see the grow room when the unit will inevitably need servicing. Will a portable aircon unit be suffice for my new grow room? Can anybody offer me any advice with these and what variables I need to take into consideration if I use one? Should I blow the air from my exhaust fan outside or is it ok to continue as I am and just blow it back into the same room?