Hello, I only use this because of the smoking. I discovered the system in a coffee shop in Amsterdam. And had nothing to lose. I have a smoking room about 20m2. And my visitors say: "The only smoking room that doesn't smell of stale smoke".
Nevertheless, I leave the windows open from time to time. And the unit runs 24 hours a day at medium level. The unit is quite loud, so I don't use the maximum level.
I think it depends on how much you smoke and how often you change the filters.