So if one person who didn't smoke walked in everyone could stop smoking and remove all the second hand smoke from the room instantly ? Yeah, that would work so well.

If you have some venues that have smoke allowed and others that do not then you limit the places where non-smokers (particularly the ones who have medical reasons for not coping with smoke) can go. Is that fair ? No. If you allow some venues to have smoke and others not then all the smokers go to that place and nothing changes. is that safe ? No.

Life isn't fair. Deal with it.