Question: I've recently purchased a Sierra woodstove with a 6" dia. outlet. I intend on venting it up my current inside masonry chimney which is terra cotta lined 8" x 16". The woodstove will be installed in the basement. My question is about sharing the chimney with a 1986 Bard fuel oil burning furnace which is vented into the terra cotta lining. Is it acceptable to line the chimney with 6" stainless steel for the woodstove, and allow the fuel oil furnace to vent around the new stainless. There are two extra capped off ports in the side of the chimney already, and I plan on making use of one of them for the woodstove liner. Answer: It really depends on the chimney capacity. Some state codes do not allow for the venting of solid and liquid fuels into the same chimney. However, keep in mind that there are fully approved Multi-Fuel (Oil/Wood) furnaces and boilers which are UL approved to vent into one chimney. If the chimney was built just for the oil burner (6-7"), then it surely will not have enough capacity for both appliances. If it is a large old chimney, then it may be OK. Best bet might be to either: 1. Drop two pipes down the chimney, one for each unit 2. Drop one larger pipe down the chimney, with capacity for both units and hook them to it. Conventional wisdom is to hook the oil furnace in higher than the wood one.