small cl grow box

i have a small cfl grow box an i have a one fan for fresh air i was told u only need a exhaust fan for small grow is this true

http://www.bghydro.com/BGH/static/articles/0606_vent.asp

Copy and paste the above link into your browser...some good advice on venilation, fans, filters, ect....i have a cfl grow running 15-23w with 2 260 cfm fans 1/intake and 1/exhaust. I also have a 260cfm oscillating fan (4'x2'x5' tent). Temps avg 72-82. I'm 3 months in to this my 1st grow with no probs. Hope this helps......

and yes, its pure physics, as air is pulled out of the room, the underpresure will automatic fill it agin, from every opening..

as a basic rule of thump your passive intake need to be 2-3x the size of the out take ventilation ..

only reason I would use a intake ventilation is to help pull fresh air in from antoher room/out doors useing ducting/tubes ..