I have a gas log fireplace on the main floor and a woodburning fireplace in the basement. There is no second floor.
I've never used either but had the chimney inspection done this year. Of course they found lots of expensive repairs needed but since I don't use either, I just had them remortar the top to prevent water intrusion.
But there are 3 flues? Why do I had 3 flues for 2 fireplaces? And which flue goes to which fireplace? (I asked the inspection techs but they didn't know.)
This photo shows two flues well and a little bit of another.