To state again, a pre-fabricated fireplace system is also known as a "zero-clearance" fireplace. This is a fireplace made from a kit, that does not require any masonry. The components can be placed very close to combustibles  without catching them on fire. These systems are common in apartment complexes, as well as single-family Dwellings. In the trade, we use round brushes that are soft to clean the flues, which are round metal piping. Over the last 24 years I have had possibly 5 customers that had the operating manual for the system. There is a right way (and a wrong way) to use these systems. Stay tuned for more data on operating these systems.