tnb narutals advertises for a 12x12 room, or a 6x6, so one in a 4x4 area should help out, I'm trying this now. Only vent after lights out. Plants can take higher temps with co2 so thar helps with cooling issues, no vent 85 to 90 in my tent with humidity around 80 to 85 percent, with lights on, temp drops to 70s with 35 to 55 rh at night, vent until hour or so before lights come on. This is how I'm using co2 for first time. Tried yeast and sugar, baking soda and vinegar, they burn out too quick for my liking. So far tnb has been the only thing that made a noticeable difference. Good luck