The nose, knows!

Yesterday morning my wife and I got in our tandem stand. The wind direction ended up being poor yet we had 10 or so deer come through from directly down wind. They never blew, never acted weird, just made their way right under/past us. A little while into the hunt, my wife started getting bit by mosquitoes, so I turned my thermacell on. 15 minutes later a doe came in down wind, and immediately started blowing and stomping. An hour went by and a group of 3 more doe came through and stopped and blew too.
I can't help but think it was the thermacell, we saw so many come from downwind before I turned it on that never even paused and looked around, then shortly after turning it on, they wouldn't come inside of 50yds without blowing, and cutting around us. Has anyone else had any issues with thermacell?

Been using a Thermacell for years and never spooked a deer.

Air rising early, not rising later?

To keep the bugs away, I usually just get a long weed and sit with my hands in my lap, holding the weed up around my face. If they fly around me, I just slowly move the weed around to keep them away. That plus long sleeves usually do the trick. I don't think the deer see it because I'm only moving a piece of weed about 6 inches max, and then only slowly.

I've used one for a few years and never spooked deer.

I've also shot a deer while my dad was eating vienna sausages, drinking a beer and smoking a cigarette.

I guess the deer in my area aren't easily spooked.

Were the deer that were not spooked young? Maybe they smelt you but didn’t know what you were so just got out of there. If an old doe smells you it will know what you are. If those deer have been spooked around that stand before they will remember and see if your in it. Even if your not in it they will blow when they go by it to make sure your not in it. I have had this happen before too. There are so many things that could possibly be a factor.

Numero uno is wind direction. I NEVER hunt a stand when the wind is not right. Do so and you'll educate deer and burn out that set-up. I would have never gotten in the set-up if the wind direction was wrong and, if it changed while I was in the stand, I'd hightail it out of there first chance I had.