My opinion, the lung room will ALWAYS have some odor to it. Always. There's just no real way to fully escape it, other than maybe having some sort of really expensive air ionizer in that room. Those carbon filters only "reduce" odors in the air it is filtering, but, since you're dumping your filtered air into the same lung room, you're not seeing any benefit to the filtration.
If you were to have that exhaust plumbed to another room, or outside, and THAT air was also passed thru that filter, you'll notice the "reduction" of smell in that exhausted air. The lung room itself is still gona stink a lil bit, and it'll happen every time you open the tent.