I don't think there is anyway of knowing. It may be harming you. Since your size is so much greater it's not considered a problem. I think their are a lot of harmful things introduced to us but it falls into that "it not doing that much harm" category.
I take it this is one of those burning incense? If so, than I would think the carbon monoxide might be the big concern for the snakes but this is all speculation on my part.

I from time to time use an air freshener in my snake room but never gave it any thought.
Good thread to start