11/26/24 During evaluation of furnace I kept smelling gas, opened furnace up to inspect heat exchanger, located what seems to be a potential failure in the heat exchanger which is unsafe. This can cause carbon monoxide to enter the airstream. Inducer motor flue had lots of build up, system would run for 15 mins and then shut off on role out. Tested airstream for carbon monoxide and was getting extremely high readings. Today I shut the Gas valve of to the furnace due to unsafe operating conditions. Need to return with Brian H to further evaluate furnace