Birds could have made nests there or parts of the chimney could have collapsed.
Chimney cleanout door installation.
8 x 8 cast iron chimney clean out door with flanged frame for masonry installation.
Installing a cleanout door on the outside of your chimney gives you clear access to the bottom of the chimney to remove ashes and soot.
Flanged frame for masonry installation 10 2 x 10 2 door measures 8 x 8.
The horizontal tee connects through the wall to a boiler on the other side.
If i had hired a pro to provide and install a door it would have cost at minimal three times or more than what my investment was by doing it myself.
This metal chimney vents an oil fired heating boiler.
Otherwise the flue may be blocked.
The doors are available through online.
Use a mirror to inspect the interior of the cleanout door and flue.
Here shown during installation you can see that this metal chimney includes a removable cleanout door at the bottom of the tee used to turn from horizontal to vertical in the chimney run.
If your chimney currently does not have a cleanout door it is necessary to create an opening in the side of the chimney.
Check the contents of the inside of the cleanout door.