clean out doors rusted off

[Lanny Freng]

Typicall masonry fireplace 1 flue, in the basement at the base of the chimney are two doors that are rusted off. Bit of a moisture issue in this area of the basement. Question is are these doors required or could they be sealed off with concrete if the ash trap door is disabled or do new ones need to be installed. I found some info that said that an ash pit is not required as long as the fireplace can be emptied at the firebox. Not finding much else about the topic anywhere. Are there any draft concerns that these doors play into? Any help is appreciated.

[John Kogel]

While we wait for Bob H. to check in, I will say that the ash pit does not or should not contribute combustion air to the firebox. So it is an optional feature in my mind at least.

The ashpit door in the floor of the fireplace may be rusted as well, so that should be checked.
I would recommend simply replacing the cleanout doors, because that way the base of the chimney is accessible for inspection, even if the firebox is sealed off.