The short answer
The main filter in an air purifier — the HEPA or MERV-13 panel that does the actual particle capture — should not be washed. Washing it damages the media and destroys the very properties that make it work. Only the pre-filter, mesh guard and housing can be cleaned. That distinction is the whole answer, and the rest of this page explains why it matters.
Why you can’t wash the main filter
MERV-13 and HEPA filters trap fine particles two ways: a dense pleated fibre matrix, and an electrostatic charge on the fibres that grabs particles smaller than the physical gaps. Water and detergent undo both:
- Collapse and mat the fibres, opening gaps that let particles pass straight through.
- Neutralise the electrostatic charge, permanently cutting capture of the finest and most harmful particles.
- Trap moisture, which grows mould and pushes musty smells back into your room.
A washed filter can look perfectly fine and still perform terribly, because the damage is invisible. It is a false economy — especially when a standard replacement pair is only around £58–£75. The same applies to combined HEPA-and-carbon cartridges from brands like Dyson, Philips and Levoit: water ruins the HEPA layer, and you cannot rinse carbon back to life either.
What about “washable” filters?
Some cheap purifiers advertise a “washable” or “permanent” filter. These are almost always coarse particle filters — closer to a pre-filter in performance — not true HEPA or MERV-13. They can be rinsed because there is little fine-particle capture to lose in the first place. Don’t confuse a genuine high-efficiency filter with one of these; if a filter claims a real HEPA grade or MERV number, assume it is not washable.
What you can safely clean
| Component | Clean or replace? | How |
|---|---|---|
| Main MERV-13 / HEPA filter | Replace | Never wash; swap every 6–12 months |
| Foam / mesh pre-filter | Clean | Vacuum, or rinse and fully dry before refitting |
| Mesh filter guard | Clean | Wipe or rinse; protects the main filter from damage |
| Housing / fan grille | Clean | Wipe with a dry or barely-damp cloth (unplugged) |
Make filters last longer (the right way)
- Fit a pre-filter or mesh guard to catch hair and big dust before it reaches the MERV-13.
- Vacuum that pre-filter monthly — that’s the part you can clean.
- Keep windows shut on high-pollen and smoke days so the filter isn’t overwhelmed.
- Buy standard sizes so a fresh filter is always cheap and in stock.
Cleaning the pre-filter genuinely extends the life of the expensive main filter, so it is worth doing monthly. When the main filter is finally spent, replace it rather than reviving it — see how often to replace a filter for the signs, our HEPA H13 guide for what the grade means, and the replacement filter guide for costs. Carbon filters follow the same rule — they cannot be washed or recharged, as covered in the activated-carbon guide.
The cost argument against washing
People try to wash filters to save money, but the sums rarely work. A washed HEPA or MERV filter that has lost its charge might capture a fraction of what it did, so you are effectively running an unfiltered machine while believing you are protected — the worst of both worlds. A standard replacement pair costs only around £58–£75 and lasts most homes a year, which works out to pennies a day. Set against the health reason you bought the purifier for, reusing a damaged filter is a false economy rather than a saving.