What Type Of Chimney Could A UL 127 Factory Built Fireplace Utilize?

What Type Of Chimney Could A UL 127 Factory Built Fireplace Utilize? Fireplaces listed to UL 127 can be constructed of metal or masonry, and are meant to use a factory-built chimney. UL 127 testing is done with a fireplace installed into a plywood enclosure with thermocouples arrayed around the structure. What is a factory-built