Carbon Filters for a 6x4

Hey guys quick question. I was just curious, what size carbon filter would be a substantial choice for a, oh, lets say a 6x4 room? Your feedback would be very much appreciated.

I mean...how tall? Assuming you have an 8 foot ceiling, that would be 192 cubic feet...so if you wanna exchange the air a couple times a minute, I'd go with a filter in the 6" 400cfm range with an inline fan to match that CFM, or have a CFM rating slightly lower than that of the carbon filter.