activated carbon

Does anyone know where to get activated carbon for less than like $4/lb? Im wanting to do a DIY carbon filter but filling a 5gal bucket requires alot of carbon. Im going to be filtering a 10x10 room would this be a sufficient size or would smaller suffice?

You really need to compute the cubic area in order to determine what you need. That sounds like overkill to me. A 5 gallon bucket would refill my filter 5 times and my room is roughly 8x8x8.

What kind of filter are you using?

It is a self contained recirculating filter. It has a large PC type fan that pulls the air through a filter (tube filled with activated carbon) and also has a fabric pre-filter on it similar to the material used to make furnace filter..