You will definately need this when flowering
A word of caution when selecting the filter of your choice.
If you are growing an exceptionally odiferous strain (i'm flowering 5 Ak-47's), you will want to use the real deal can filters.
I previously had 2 Goblin charcoal filters which use coconut fiber carbon so that it is lighter than say the Can 100.
I have a sealed room and could still smell the girls in my air vents.
Once I got the Can 100, I have to walk in the tent and inhale as hard as i can to smell them now.