Can I ask that people in Krakow really need "smog masks" in winter? Is it exaggerated?
Yes people wear smog masks, not everybody, but certainly anybody who's well informed about the heath risks of smog. The air quality in Kraków during the winter is simply appalling. It's not coal mines that cause the pollution. It's coal fired electricity and the burning of coal in commercial and domestic settings for example coal fired central heating or people burning poor quality coal and rubbish in their stoves at home.
Aren't you the guy who got a job in IT in Kraków? Have you considered Warsaw? The air quality there is better than Kraków though there are still very bad days in winter but it's not on the same scale. Plenty of IT jobs in Warsaw so you might want to think about it, also it has the highest salaries. Gdańsk has an IT sector too and the air is best there because it's by the sea.