Question. I ws on a Bryant 350MAV 90% furnace yesterday and the flames looked funny so I took a reading in the exhaust and it was 1392 PPM. Secondary heat exchanger is bad. Roll out switch was not tripped but the burner box was extremely hot. I had my own business in Minnesota and by code you are suppose to red tag furnace. So I called Bryant here in Indiana nd they told me as long a it is not entering into living area I should leave it on for them to have heat. Of course I was shocked about this and felt uncomortable but the other tech said to leave it on for them also. So I left it on even though I was uncomfortable with this. The other tech said since Bryant had a enclosed burner compartment and the inake was vented outside it was ok to leave furnace running.