Station 67 reponded  to a Co Alarm on Rt 819 at appx 7 am on 10/9 . 2 patients were reported  with the intial dispatch. Engine 67-2 arrived on scene and found 2 patients and Co Levels approaching 400 Ppm in the upstairs of the residence. Both patients were taken to a local hosipital for treatment. The cause was found to be the flue pipe rusted of the wall at the chimney leaving Co into the house at a extreme high level.Crews operated on scene for just over 2 hrs.