Here is a Holmes airfilter.I put about a 1/8" layer of Marineland activated carbon over the long ago spent carbon sheet that came with the unit.Since the Carbon is so cheap I change it out every month.I tested it out to 45 days and this is when the smells start bleeding thru.I just clean out prefilter,dump carbon,clean old carbon sheet,inspect pleated Hepa filter underneath,and put all back with new layer.
I do not vent outside so this is a same room stand alone filter.I would not do this if it did not work.I have friends come over unaware of what's goin on less than 15ft away from them.Most important of all my main bro is a Leo,and respected member of the community.I know he would not tell on me,but I do not want him worrying about me either,and I also limit my public exposure with him out of respect.
I do not grow super dank aka skunky strains (that is another debate I will not get into) so I can get away with a timed 3 hr on 3 hr off cycle to save some electricity.If this was not my own place,or growing some Chemdawg or something then 24hrs it would be on with a strict monthly change.Granted I run a perpetual cabinet,but if I did nothing it would definately hit you when you come in the front door.
Security is very important,but just like growing in general:research goes a long way.