Carbon scrubber question

Ok I have a couple of questions about this carbon scrubber that I plan on building https://www.gardenscure.com/420/security/60127-ryoko-builds-diy-activated-carbon-filter.html
Once I attach the scrubber intake to the top of my growbox, do i just direct a fan pointing up toward the intake? Or mount a fan under the intake to where it is sucking the air into the filter? Basically, what kind of fan should I get and how do I mount it?
Next, will the air simply be forced through the filter into the room smelling fine? What if I put a couple of them on top of my grow box would it solve my heat problem? I haven't built my box yet so I couldn't tell you the size but I will probaly use a 400 watt hps so while I'm at it, any size recommendations for a container, assuming I want to grow the max amount of plants a 400w hps allows(how many would that be?) Thanks any answers are appreciated.

you put that thing in the grow room then run a slow inline fan on the open end of it, then attach tubing to that inline fan and then aim the tubing where you want(attach it to the laundry dryer/to a hole in the ceiling, etc)

I bought one of these...is the cheapest and best unit i've found..no building necessary..., and is all self-contained..and is much better looking than a home-brew unit. With these , you don't need to run a duct/vent outside of your grow area either.
eBay: Activated Carbon Air Scrubber Odor Filter Shelf Unit (item 130064065112 end time Jan-08-07 18:00:20 PST)

This is also another cool little unit:
eBay: AIR SCRUBBER ACTIVATED CARBON ODOR FILTER HYDROPONIC X2 (item 150078815853 end time Jan-08-07 18:00:00 PST)