Listen to your gut! I was on the phone with a friend last night talking about all kinds of things including how it has been great fireplace weather. I have a wood burning fireplace, she's got a gas one. After about an hour of chit chat we were getting off the phone and she happens to mention how the last few times she's had a fire she "felt a little weird and had a little headache" and she wondered what it could be. 1/