Using a 10x10 spare room for grow room. I've got a 4x4 area blocked off to veg and flower. The only fresh air I will be able to get into that room will be from central HVAC. I have plenty of fans to circulate the air but no way of doing air exchange from outside. I will be able to leave the door to that room open on occasion to bring in air from other parts of the house. I realize this is not ideal but will it suffice?