It is important that you never wash your UltraHEPA or Carbon/VOC Filters. Doing so will damage your filters, making them unusable.
Can I wash my Pre-Filter?
Your Pre-Filter was designed to be reusable. Avoid washing your pre-filter as you do not want to introduce any moisture onto the filters.
We recommend vacuuming your Pre-Filter monthly for best maintenance and to extend the life of your filters until the next filter change. See Can I clean my Pre-Filter?