I don't know the full intent of the law/regulation but this is the info from him: "Systems venting oil and wood in the same flue from before 1998 are completely grandfathered. I was told that the regulation allows for the heating system to be replaced and still vent in the same flu. However, I was told that the wood and oil must be on the same floor, canâ€™t have an oil furnace in the basement and a wood stove upstairs. I was also told that the two thimbles must be at different heights in the chimney and that the wood thimble must be above the oil. I was also told that the wood burner must be a manufactured unit and if not UL approved must be installed or inspected by a person with a heating license. No more homemade furnaces or barrel/rim stoves. Iâ€™m not worried about being not being legal. I spoke with the fire marshalâ€™s office, my insurance, and a licensed plumbing and heating contractor. According to them, Iâ€™m all legal." That being said the oil burner he installed has the ability to be direct vented and he may end up doing so. In order for the stove to work properly the oil burner isn't going to be running properly and vice versa. I can tell you that venting an oil burner and a wood stove in 1 chimney is very common in the area I grew up in. My parent's place was like that, both the house and my Dad's garage/shop. The stove he is using is make by Johnson Energy Systems out of Milwaukee, it's from 80s-90s. Not UL listed, but again was signed off by the above people. It looks kind of like this one: http://www.purplewave.com/cgi-bin/mnlist.cgi?091118A/4313 I think that might be a little bit larger model though.