Essential Oils -- Safe or no?

[kyanite]

I have a diffuser where you mix one or two drops of essential oil with water, and light a tea light underneath to let the scent diffuse in the air. This would be used in a room the birds rarely come into and would never be lit while they were inside. I would only use it with the door SHUT and the window open. The birds live down the hall. They very, very rarely hang out in my actual bedroom, and if I were to bring them into the room, I'd wait until I couldn't smell it anymore, and have aired out the room for an hour or two. My question is: do you think I'm being cautious enough? Or should I just completely nix the idea of ever having a scented room? I love my little gemstones more than anything, and I don't want to put them in harm's way.