Question: I have a metal insulated chimney on the outside wall of the house which extends below ground level to the basement where a elbow is connected and a pipe extends about four feet through the foundation and into the basement this has a cap hanging on it and is for clean out. about two feet above the elbow the pipe from the oil furnace tee's into the chimney and on the first floor the wood stove pipe exits throught the wall and tee's into the chimney. I have not used this wood stove yet but would like to what are the guidelines ? Answer: First of all, no insulated chimney that I know of is rated for ground contact. That means it should be open around the pipe, or framed in with masonry, in the area where it goes below ground. Also, there is not supposed to be 90 degree elbows on insulated piping, just an insulated "TEE" with a cleanout. As far as multiple units and different fuels into the same chimney, this is also dicouraged. It is legal in some states as long as the chimney has capacity, but in practice, it's easy to get it wrong. Take your example with the stove located upstairs. If the stove clogs the chimney with creosote, the oil furnace will continue to vent into the chimney...and then back up, possibly sending deadly carbon monoxide into the home. In summary, you should have it checked out by a qualified professional.