To be exact: the problem here is fossil fuel and wood being burned in inefficient furnaces/stoves/fireplaces where the fuel doesn't fully burn. There are efforts by the government to replace them but they aren't super effective yet (random example: https://um.warszawa.pl/kopciuchy).

For the industrial scale fossil fuel furnaces this problem is solved already (they are obviously still bad because of their huge CO2 emissions but that's a different problem).