does my window ac unit replenish air (do i need to add c02?) closed system

I'm wondering if my window ac unit will bring any fresh air (c02) into my grow room or if I need to add c02 to it ---- im using 2 rooms.

1 for vegging with low cost cfls/ hydro / no water chillers and a 12k btu ac.

then 1 for flowering thath as water chillers, 24k btu ac, and c02 in liquid form.

Will my vegging room be able to get by without the c02?

what if i just leave the door cracked most of the day... or wide open a few times a day?

or will i need to install a fan to blow new air in few times a day?

thanks
j