You make a really good point billyboat about different strokes for different folks. Additionally, thats a good thing to take into considering, the smell leaking through air cooled reflectors. I never thought of that although I run a 8in. scrubber inside the room and another one on intervals outside, just in the general area.
I use the following:
1. scrubber for drying room, only on when material is in there
2. scrubber for grow area, runs 24 hours when plants are in there
3. scrubber for common area, on timed intervals 15 mins on every hour
Although the thread isnt about clean air, the point you made was important. If I were to constantly circulate air within the basement running through lights, the air in the basement would be scrubbed 24 hours.