general question about carbon filters

so i have had 4 big girls for a while and the smell is really on the DL.

my question is should i have the carbon filter outside the grow room(exaust)

or should i have it in the grow room to kinda recirculate and re filter the air?

thanks

You can do either. I recirculate because a I run co2. But you need a bigger fan to do that. Remember you want the air pulling through the filter not pushing air through it.