mixed fuel venting?

Venting oil furnace exhaust with wood burning, ok for combined venting in chimney flue?


As long as the flue pipe is not galvanized.


Violation of NFPA Standards

Each should be vented into a separate flue. Multiple connections can cause flue gases and sparks to pass from one flue opening to another, reducing efficiency and igniting unburned gases in the flue.

In my past life I installed a number of “Longwood” wood burning furnaces with oil starters and the manufacturer’s instructions were for a single flue of specific materials. I don’t remember the type of material, but I recall that it was not uncommon.

Manufacturer’s specifications prevail over any other…


Mixed Fuel Furnaces and Boilers (Woodsman, Longwood, Eagle, etc…) are designed for this application as a single unit.


An Oil Boiler/Furnace can not share a flue with a Wood Stove or wood burning Fireplace.

Went back and took a better look at the first post…I didn’t pick it up as two separate units the first time. And I don’t even drink “darn margaritas”.
What can I blame it on, other than old age???

Thanks guys.

They are seperate units with the boiler in the basement and a wood burning stove on the first floor.


some folks have gotten blessings to have one connected/used at a time, but never both in use at the same time… I would not recommend that, but occasionally the local jurisdiction has blessed it…

separate flue per fuel is the safest!