larryfoster wrote:If there were something that bad with the chimney wouldn't my house filled with smoke?
It's not so much the "level" (yes, it is being ZERO), which means combustion gases can ONLY go into the house, but that it is changing without you knowing WHY.
You could have an obstruction or something happening that sounds like it is opening and closing. What if it slams shut and stays shut while you sleep?
Being awake, with a CO monitor, watching the smoke or lack of it, etc is one thing. But it's getting to be night and the fire will likely smolder for quite some time.
If you cannot maintain draft, you should not be trying to burn anything.
I'm not an alarmist, but the situation you describe is one I am NOT comfortable with. Hopefully it is something simple- would be great if it was just a bad mano, but is there another one to check it against? Err on the side of caution, buddy.
You said you were going to have your chimney checked and cleaned, right? Good idea. Do that.
Going to zero draft = shut it down. I don't know what else to tell you, except that you CANNOT safely fire with zero draft.