I've decided on building a grow room that is 6' x 5' x 3' for a closet. I plan on running a 25' tube into one side for air in (aluminum flex tube) and another 25' out with segments of carbon air filters inserted in at multiple points to kill the smell. Is it better run a squirrel cage blower on the inside running air out through the filtered tube or to run it outside blowing the fresh air in? What is a solid strength of CFM on the blower?

Second I plan on growing around 6-8 plants. Will a 400watt HPS be enough for them all or will it require something stronger?

I begin in a week an a half and will begin posting photos in a journal.

a 400hps should work for 6 plants