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, but if you choose to wash your Pre-Filter, you must remove it fully from the Carbon/VOC filter, hand wash it with a gentle soap, and allow it to dry completely before reattaching it to Carbon/VOC filter. 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?