Chimney Breast Areas are Extremely Damp in 1890's Flat Conversion

[UKDIY123]

1890s building, maisonette style "flat conversion". Chimney breast areas are extremely damp. If I run my hand over the wallpaper, my hand is actually wet. Surveyor chap says "put air vent bricks in". (Presumably he meant indoors.)

I think the stack is capped, with one air brick on the outside of the building.

In the other upstairs bedroom, there's another chimney breast area, but that stack has been removed. I have the same problem though - excessive damp. There appears to no outside air brick for this area.

Should I put 2 air bricks in, indoors, for each breast area? (I'm thinking there's 2 cavities per breast area.) How about downstairs too? Even a picture hook there has gone rusty, in the chimney breast area.

(That would be a total of 8 air bricks.)

Thanks a lot for any comments/ideas/etc!