zatęchły in English:

This room smells musty.

two musty mattresses for the entire family to sleep on

a dark musty library

As we stood there in that musty old mill, Mr. Darby repeated the story of the unusual conquest, and finished by asking, "What can you make of it?

Chills went up and down our spines when we walked down into the dark dank cellar

The air in the basement was dank.