Though I don't do much hunting from a stand/blind these days, I used an Ozonics HR-200 extensively for several years and had a lot of success with it. Among other animals, I harvested a black bear and a whitetail deer that both circled directly downwind from my blind and I'm confident both would have caught my scent if I weren't using the Ozonics. The bear sat about 20 yards downwind of my blind for over an hour one before heading into the bait (I was hunting on the Quinault Reservation) and offering me a shot.
Nothing is 100% guaranteed to eliminate your scent all the time. The Ozonics isn't cheap and it only works if you're in a fixed location like a deer stand, but this is still the most effective product I'm aware of for reducing your scent while hunting.
For more information, visit:
http://thebiggamehuntingblog.com/gifts-for-hunters
