I have a zero-clearance wood-burning fireplace that has a throat that is
deteriorating and breaking. The throat damper was removed and replaced with
a chimney top cap/damper before I bought the home because it was so rusted
it wouldn't open. The throat (if this is what it's called) is a metal
housing that is located between the beginning of the chimney and the body of
the fireplace (the hearth?) where the throat damper used to open. It is
shaped like a squared upside-down funnel, with a ledge toward the back.
There sits debris on this ledge that looks like rock and stuff, residing
there from the building of the chimney, I suppose. Looking further up the
chimney, it appears that there is a metal lining going all the way up too.
Just above the ledge, parts of this metal throat have chipped away from
becoming so rusty, and exposed the brick behind it. There is a small hole in
it, about a 2" diameter. No fire ever gets up to the ledge, but flames do
sometimes rise near where the throat starts. I'm concerned that either smoke
or creosote could be penetrating behind the housing, into the brick layer
behind the throat, causing some danger. Should I be concerned about this and
call the chimney expert, or is this something that will not affect the
safety of the fireplace?