I used mine here in NH last Fall while hunting bear, they never noticed a thing and it works on the black flies on my Spring turkey hunts. I had two cubs come in downwind and were hanging around a good 30 minutes or so. With in minutes of me turning off the therma-cell before heading home (so it will cool off) and I was attacked by every flying biting blood sucking insect in the woods that evening. I use my just so I can grill on the back porch seeing I've got two hatcheries near my house, a pond in the front yards and a river in the back[] The thing works!