I am an Hvac Contractor, I was very surprised the other night when my wife was finished cooking to have the co detector go off. I pulled out my Bachrach system gave the house the go over and discovered it was my oven puting out 40ppm of co. Is this unusual??, common?? I deal with furnaces and ac units. anyone want to get me up to speed?? thanx "Im appealing to the collective"