2/13/2020: Wiping a dry microfiber cleaning cloth over a treadmill running belt using a vacuum to collect loose debris can be used to clean the treadmill running belt surface. A damp cloth may also be used to wipe down the walking belt.
Do not use a wet mop to clean a treadmill running belt. Water could make its way to electronic components causing damage, or seep in between the running belt and deck causing the product not to function properly.
See the following articles for preventative maintenance best practices: