1. Are they safe to use in a ground blind?
2. Do deer notice them?
3. Do they work for biting gnats and other insects?

Any other comments that I might find useful.

Thanks

I have used a T-Cell a lot and love it. It's one of the few gizmos to hit the market that actually works as advertised.

To try to answer your questions:
1. Yes. Now I wouldn't hold my face over the appliance and huff that stuff, but you're not going to poison yourself or asphyxiate in a ground blind.
2. Probably. But it's a naturally occurring substance and I've not noticed any deer spooking when I used it. But if a deer can smell the T-Cell, they can smell you, which is likely the bigger problem.
3. All I know is I stop getting bit and/or harassed by bugs when I use it. Even if it doesn't directly affect biting gnats or other insects, its performance on mosquitos alone makes it worth its weight in gold.

https://wildernessinstinct.com/is-thermacell-safe-to-breathe/

Thanks. Looks like I’ll add it t my hunting checklist. I’ll know by the end of the day on 9/16 unless it’s cold and windy.

FWIW, I'm an absolute bug magnet and the Thermocell + ground blind combination will let me hunt in comfort just about anywhere there are mosquitos. It's a better mouse trap.

Just buy it and move on. Great product.

Great product, I don't hunt without it.

I hog hunt the river bottoms in East TX and if I forget my Thermocell or it doesn't work for some reason, I go home.

Don't even question it. Buy one...or two. I couldn't survive hunting early season without one. The only caveat that should be mentioned...if it is windy, the thermocell won't be as effective.

And watch for sales on the refills.

One of the best inventions of the last century in my opinion. I use the heck out of mine.

"Earth Scent" refills are available but I've seen no evidence they spook deer any more or less than the normal refills.