Totally bricked up fireplaces, or with vents installed?
Smoke testing from the open fireplaces will tell you something, & might establish a pattern
However, you must be certain for safe venting of fumes. For you, or someone after you, might install an appliance that requires a specific kind of terminal.
Typically, all the pots on your side of the shared stack are yours. But you have rogue pots at either end.
That stack, as your earlier post mentioned, requires re-building & re-flashing.
Whatever happens, eventually you want to open and sweep and smoke test and properly vent at the terminals all your flues. Research why & how on here.
Just guessing: but are you on the Sandymount rd, or the airport rd?
You are probably in Kerry!