Refers to the black powdery substance produced by the incomplete combustion of organic matter.
El hollín de la chimenea se acumuló, y tuvimos que limpiarlo antes de la cena.
The soot from the chimney accumulated, and we had to clean it before dinner.
El yunque estaba cubierto de hollín después de la intensa jornada de trabajo.
The anvil was covered in soot after the intense workday.