Gas furnace intake and exhaust pipes

[Robert Huffman]

When inspecting a Ducane gas furnace I saw that the fresh air intake and the exhaust pipes came together in one pipe just before exiting the basement wall. Is this acceptable?

[Gunnar Alquist]

When inspecting a Ducane gas furnace I saw that the fresh air intake and the exhaust pipes came together in one pipe just before exiting the basement wall. Is this acceptable?

Sounds like your question refers to a category 1 furnace. If that is true, then there are concentric intake/exhaust vent pipes that are specifically designed and approved for that. I guess the primary advantage is that you only have to poke one hole in the roof. Search category 1 concentric vent and you will see examples.