Metal chimneys: are generally
installed within wood chases (an enclosure that looks somewhat like a
chimney). The chase is an enclosure which may or may not be required by
some jurisdictions. The double or triple-wall chimney vent pipe may be
entirely exposed to the weather. The pipe is almost always exposed in
attics. The integrity of the metal chimney is very important since a
direct vent "fireplace" vent cap terminates outside the same
wall the unit is installed against. Separation at a seam or connection
would almost certainly result in a fire within the wood chase or attic.
Check with a mirror and flashlight often. If you're not sure of what
you're looking at you are advised to contact a qualified chimney
specialist before each season of use, or at least once per year.
Termination requirements of metal chimneys are the same as for masonry
chimneys. A simple vent pipe atop a wood stove qualifies as a metal
chimney. These are often single-wall pipes prone to rust-out and other
failures. These must be checked before each season of use and monthly
thereafter.