RE: How far?
That's one reason I seldom use scents when bowhunting. You're trying to keep deer from smelling you by playing the wind and then try to put out scent that can only help you if a buck smells it from down wind.
Rifle season is a different story, though. Put that scent out 50 or a 100 yards on a right angle to the wind and watch out. It worked for me last year on an 11 point. It was actually the first time it has worked for me.