Compared to smoke there is a lot less stuff in vapor. Vapor consists of the essential oils in the plant, where smoke is everything, including the plant. We do feel that if you leave the vapor in the bag for hours at a time, gravity will have the vapor particles settle to the bag making the vapor not so good. If you are vaping in a bag, try to avoid filling it with more than you will immediately use. You can always fill the bag up more. This is good for any forced air vaporizer.