Diagnosis
You're right to be cautious. The sealed HEPA/Carbon filter assembly is not user-replaceable on the HP07, but the pre-filter wrap around it is designed for regular washing.
How to Fix It
Wash the outer pre-filter. It's simpler than it looks.
- Unplug the machine and let it cool completely.
- Press the two grey release buttons on the sides of the base and lift the entire loop/purifier assembly off the base.
- Turn it upside down. The grey fabric wrap covering the purple inner filter is the pre-filter. Gently peel it off starting from the seam.
- Rinse it under COLD water only. Do not use soap, detergent, or scrub it. Gently squeeze out the water—don't wring.
- Let it air-dry completely for 24 hours. No heat, no hair dryer.
- Snap it back onto the purple core, reassemble, and you're done.
If That Didn't Work
If the machine still shows a filter maintenance warning after cleaning and a reset, the internal sealed filter's lifespan is up. Unlike older models, you cannot buy a new one. You must contact Dyson for a filter replacement service.
Heads Up
Never, ever try to wash or get water on the purple inner core. That's the sealed HEPA/carbon filter and water will ruin it permanently, triggering a fault code.