Damp patches by chimney breast; cause and best solution?

Hi, I have lived in current home 10 years and just recently discovered low down damp patches either side of the chimney breast in the living area. There is no chimney breast in the room above, this was all removed at some earlier time. The fireplace is ‘open’ in the living area but just ornamental. Could this damp be due to condensation even though it’s open as heat from the room has nowhere to go, and if so what would be the best solution? An outside airbrick? Vents in either side of the chimney breast?