Question: I live in Massachusetts and have been told you can run both appliances into the same flue. I have tried to researched this and have found no definite answers. Here is what i have: oil fired forced hot air furnace †venting into 8 x 8 masonary chimney. Also have Jensen 24A wood furnace venting (6" pipe) into same flue but it is vented about 24" lower than the oil furnace. Given these are not going to be used at the same time, and that the chimney is cleaned each year. I have been told it is "grandfathered" that it is ok only if the oil is vented above the wood. Any help or info would be greatly appreciated. I also have a fireplace in the living room but want to put a large woodstove downstairs (in place of the Jensen furnace) to heat the house but want to find out if this is acceptable by code. Thanks for your time. Answer: TO my knowledge, Mass DOES have a code which allows the use of Oil and Wood into the same chimney. Of course, this assumes the chimney has capacity for both appliances. Tests were done years ago, with the result being that oil and wood into the same chimney actually kept a CLEANER chimney than just wood. Most other states have never studied the issue, so they simply say no since that is always the safe answer. And I have to somewhat agree - if you make a blanker statement about multiple use of flue, Joe Homeowner is often going to take matters into his own hands and do something stupid or dangerous. The most important thing is professional installation and/or inspection to make certain each job is done right.