The furnace is in the crawlspace, so I don't know if a leak from the flu would come into the house. It sure would if the furnace were installed in a closet in the house. Anyway, they replaced the whole kit and caboodle. I prefer it that way. I now have faith in the CO alarm, but not too much faith! Could it fail the next time? I wouldn't want to risk it.
One thing I learned is how remarkably clear headed, quick thinking and analytical you can be at 6 in the morning when you jerked awake by an ungodly racket 10 feet away. In a short time you think: "Is that smoke? I don't smell it. It must be CO. Okay, throw open the windows and doors. Do I have time to lower the thermostat and shut off the furnace before evacuating? Surely I do; they wouldn't make the alarm trigger when you are 90% along the way to asphyxiation. The other alarms are not triggered. Thermostat down, flame off . . . Okay, how do you turn off the unit completely?? Ah, here. Furnace off . . . Alarm stopped. Good!"
