Buy MERV-13 Filters (UK)

The best thing about a MERV-13 purifier is that the filters are a standard replaceable part — not a proprietary cartridge that locks you into one supplier at £65 a pop. Budget from about £58 a pair (two filters, lasting 6–12 months).

When to replace

• Every 6–12 months for typical use.
• Sooner near heavy traffic, building works or if you burn wood — London main-road homes are at the shorter end.
• If airflow drops or the media looks grey, it's time.

Why standard media beats a proprietary cartridge

The strongest argument for a MERV-13 purifier is not made on the day you buy it — it is made every time you replace a filter. Sealed-unit brands use proprietary cartridges: only the manufacturer makes them, only the manufacturer prices them, and if that model is discontinued you can find yourself owning a machine you can no longer feed. MERV-13 media is the opposite. It is a standard part in common sizes, so you can buy 3M Filtrete or an equivalent from more than one supplier, at around £58 a pair rather than £65-plus for a single proprietary cartridge. Over the life of the machine that difference dwarfs any gap in the sticker price, and it means you are never locked in.

MERV-13 is also the right grade for home air, not a compromise. It captures roughly 93% of fine particles — the PM2.5 that matters most — while staying open enough to let a fan move a large volume of air. That combination of good capture and high airflow is what delivers clean air to the whole room. Our MERV-13 vs HEPA guide explains why that throughput usually beats a fractionally higher single-pass rating at home, and the Corsi-Rosenthal box guide shows the principle taken to its logical extreme.

Getting the fit and grade right

Two things trip people up when buying replacement media. The first is size: measure the filter your unit or box actually takes and match it, since a filter that is slightly too small leaves gaps that let unfiltered air bypass the media. A little foil tape closes minor gaps on a DIY build. The second is grade: for particle removal MERV-13 is the sweet spot, but remember that no particle filter of any grade removes gases or odours. If cooking smells, smoke or VOCs are your real problem, you need activated carbon in addition — which is why the carbon-equipped kits exist alongside the plain particle ones.

When to change them

• Every 6–12 months in typical use.
• Sooner near heavy traffic, building works or wood-burning — London main-road homes sit at the shorter end.
• Whenever airflow noticeably drops or the media looks grey, whichever comes first.

Kits ship with media fitted, and there is currently 10% off with code LONDON10 applied automatically through the store links. If you are still choosing a unit, the pre-built kit page and the best air purifiers for 2026 are the places to start.