Reduced Performance: If the brush isn't cleaning effectively, producing less power, or sparking more than usual, it may be worn out.
Regular Inspection: Check the brush for wear and tear regularly. This can include visually inspecting the carbon brushes in motors or bristles on cleaning equipment.
Clean the Brush and Housing: Dust, dirt, or carbon deposits can accumulate around the brush. Regularly clean the housing and brush surface with compressed air or a soft cloth to avoid blockages.