Do not have that thing inside an enclosed blind with you!
I had one up wind of me on a picnic table while I was reading for about 3 hrs and it wrecked my sense of smell.
It has been almost 2 years now and I can barely smell. I'm just starting to be able to smell things again, but may not completely recover.
Some things that used to smell good, now smell like crap. Like Coffee! Not fair!
I can't smell the sweet smell of elk in the hills anymore either!
It's bad enough that I can't smell gasoline or diesel or tell the difference between them. A problem when I have both for my vehicles on a hunting trip.
Bla, Bla, Bla, just be careful with the Thermocell thing! It works great for keeping the mosquitoes away, just don't breath the stuff.