can I make a carbon filter? I've found small containers of activated coal for aquariums at walmart. could this be made into an exhaust filter? what about small electronic air filters. how well do they work with the smell? the air filter I have has an ionizer in it as well. what if I place the filter in a buffer box inside the exhaust? how well would these 2 methods work for a 4x10 room? what if I use both methods together? I've been researching and brain storming, but hearing from someone with experience can be invaluable.