Question about carbon scrubber placement

I am somewhat confused about where to place the carbon scrubber I have built. In the 101 faq section on how to build a scrubber the individual placed the scrubber inside the grow tent. I thought it was to be placed on the outside of the grow tent attached to an inline fan which draws the air out of the tent and into the scrubber thus removing the odor. Which is the correct placement for the scrubber?

In theory it doesn`t really matter as in both scenarios the smelly air is going through the scrubber. I have my filter outside my growroom and its fine, my mate have his inside his tent and it works too. If your ducting is poor quality and have leaks it would defintely be better to have the scrubber inside though.