Great advice about the degrees and such....and you are right that even if you do use scent killer, deer can and will detect you if the wind is just perfect for them, but I have had plenty of deer directly down wind of me, and they never detected me. So tosay it doesn't work at allwould be false.
And I have had plenty of deer directly downwind of me and they never detected me when I haven't used anything for scent control. Why? Wind thermals, topography, height your in the tree, young deer.
Either that or I just don't stink as much as the rest of you.