> * Alert others that there’s secondhand smoke in the area. They will smell it in a moment too. They might even be able to smell it before they see the glasses

> * Alert others that there’s secondhand smoke in the area. They will smell it in a moment too. They might even be able to smell it before they see the glasses. > * Show smokers how far their smoke travels, making the invisible visible. They don’t care about this, especially in a place where smoking is allowed. And if it isn’t allowed then the solution is to kick them out, and therefore there will be no more smoke soon and the glasses won’t be doing much.