MrStinkyanswered grow question 3 years ago If you have one correctly setup inside the tent, you will only get smell outside the tent when you open it up.
If you totally cant allow any smell detection then yes, carbon filter outside the tent too but you probably wouldnt need to run it 24/7 -maybe just an hour or two before you are expecting visitors.
You can also use ONA gel instead of a 2nd CF.