I have an apartment in Portugal that sustained severe smoke damage occasioned by smoke from my downstairs neighbour's chimney. The two chimneys vent to the atmosphere at roof level. They do not have chimney pots which extend through and above the roof.
Yes, the smoke was according to a local sweep caused by wind blowing the smoke across my chimney which was then sucked down into my apartment. The Venturi effect was mentioned. Would this be correct?