When you look into the cleanout door you should see daylight from the top of the chimney.
Chimney cleanout door installation.
Birds could have made nests there or parts of the chimney could have collapsed.
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.
The horizontal tee connects through the wall to a boiler on the other side.
Adding a chimney cleanout door requires cutting the opening and installing a manufactured door that s designed to prevent cool air from entering the chimney.
This metal chimney vents an oil fired heating boiler.
Flanged frame for masonry installation 10 2 x 10 2 door measures 8 x 8.
The doors are available through online.
Otherwise the flue may be blocked.
Use a mirror to inspect the interior of the cleanout door and flue.
Check the contents of the inside of the cleanout door.
If your chimney currently does not have a cleanout door it is necessary to create an opening in the side of the chimney.
8 x 8 cast iron chimney clean out door with flanged frame for masonry installation.