Understanding my chimney
Masonry Chimney
Masonry chimneys typically have a terracotta or steel liner. This is to protect the bricks and keep the draft entact. If the liner is damaged the chimney can be very dangerous. Burning wood will create creosote which can be ignite within the chimney and start a fire. This is one reason why all fireplaces need an annual inspection and cleaning.
Zero clearance chimneys
Zero clearance chimneys require much less maintenance than a masonry chimney. Potential issues for a zero clearance chimney could be soot build up, disconnected vent piping. or issues with the flashing near the termination.