I run an 8" Hurricane fan on a 4 foot tall carbon filter by Phresh and it works great for a space double that size or bigger. If you really want to eliminate smell I would run a carbon scrubber near each end of the grow room, especially near any doorways etc. Keeping temps as low as reasonably possible can also help with smell.. My buddy would crank his AC down to 65 lights on to kill smell when his landlord would come by.
Keep in mind when buying you will need to replace the carbon scrubber every 1-2 years depending on how bad your air quality is.. They will almost start smelling like drying paint fumes when they go bad at least with the Phresh carbon filters.