I'll admit, that part of the article made me scratch my head. I've never seen a gas furnace vented through a chimney - all of mine had separate vent stacks. Maybe this reference is an upper east coast sort of thing dealing with older houses.
Well, I live in Connecticut, that’s pretty far up the east coast. Maybe I’m missing something
The northeast seems to still be heavily dependent upon oil furnaces for some odd reason. Here, nearly all the houses old enough to have had an oil furnace have had the tank removed, soil remediated and the system replaced with natural gas. It’s a major detriment, trying to sell a house with oil heat, especially if the tank is underground. Potential hidden surprises if it leaked, and most do eventually.
My gas water heater vents through the chimney and my old furnace used to. My basement’s unfinished so the PVC vent pipe isn’t an issue.
Well, my house is in IL, was built in the early 50's, and both the gas furnace and gas water heater, which went in much later, vent to the chimney. The orig. heat was a coal furnace.