A carbon filter will filter all the smell if you lose the intake fan and just pull all your exhaust through it. Having no intake fan will create slight negative pressure inside the box, meaning any gaps will have air coming in through them and voila, no smell leaks. This applies to any growroom, as it's very rare to have one that is completely sealed, and if you have a fan blowing in there is always a chance that some odours will leak out.
Also fwiw, I wouldn't be growing in a cardboard box, little flimsy, and flammable don't you think? Wood doesn't cost a fortune, and it's a fun project to build a cabinet. You can also tailor make it to your requirements for size and layout.
Good luck.

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Originally Posted by ceestyle
Don't be a martyr wasting $100 or more on CFLs to prove they're inferior for flowering pot.