After a fire, the following substances may be left behind:

• Ashes: Ashes are the powdery residue that remains after something has been burned by a fire. They are typically composed of carbon, minerals, and other trace elements. In crossword puzzles, "ashes" is a common answer to the clue "what remains after a fire".

• Soot: Soot is a black, powdery substance that is created when organic matter is burned incompletely. It is composed of carbon, ash, and other substances.

The exact substances that are left behind after a fire can vary depending on what was burned and how hot the fire was. However, ashes and soot are two common substances that may be present.