Belt dust is a maintenance clue

A little dust is ordinary. A new line of black dust, or dust that returned a week after a clean, is a note on that treadmill. It often sits with poor tracking, a dry deck, or a belt that is glazing.

Clean it so you can see whether it returns. Write the date you cleaned. If it is back before the next weekly walk, open a fault. Do not keep cleaning it as the job.

Do not breathe it as a test

You do not need to identify the dust by taste or by blowing it about. A photo and a sentence are enough for the person who will tension or replace.

Check the neighbouring machine. If only one produces dust, the cause is that machine. If the whole row does, look at the room and the housekeeping before you order six belts.

When you replace the belt or dress the deck, say whether the dust stopped. The next dusty week is otherwise a mystery.