"HEPA filter" has become one of the most abused terms in consumer air purifier marketing. It implies high performance but carries no legal protection — in most markets, including the UK, any manufacturer can print "HEPA" on a product without meeting any defined standard. The result is a market full of products ranging from genuinely excellent medical-grade filtration to carbon fibre mesh that would barely pass as a kitchen extractor filter.
Here's what the grades actually mean and how to tell whether a purifier is using genuine specification filtration or borrowed language.
True HEPA vs HEPA-Type
True HEPA (sometimes called Genuine HEPA or just HEPA in properly labelled products) refers to filters that meet the EN 1822 standard in Europe, or equivalent US standards. The core specification: the filter must capture at least 99.97% of particles at the most penetrating particle size, which is 0.3 microns in diameter.
HEPA-type, HEPA-style, HEPA-grade, HEPA-like and similar phrases are marketing terms with no standard behind them. A filter labelled "HEPA-type" could capture 95% of particles or 50% of particles — there's no requirement. These filters are typically far less dense than True HEPA, which allows lower fan speeds and quieter operation, but at the cost of substantially reduced filtration.
When buying any air purifier, the listing should explicitly state "True HEPA" or quote an H-grade (H11-H14). If it doesn't, assume the filter is below True HEPA specification.
The H-Grade System
European HEPA filters are classified under EN 1822 into grades based on their efficiency at the most penetrating particle size:
| Grade | Efficiency at MPPS (0.3 microns) |
|---|---|
| E10 | 85% |
| E11 | 95% |
| E12 | 99.5% |
| H13 | 99.97% (overall), 99.95% at MPPS |
| H14 | 99.995% (overall), 99.975% at MPPS |
For context: "True HEPA" as commonly stated in product marketing corresponds to H13 grade. H14 is used in cleanrooms, operating theatres and similar environments where near-total particle removal is required.
For domestic air purification — allergies, asthma, general air quality — H13 is the appropriate target. H11 and H12 are meaningfully less effective and generally found in cheaper products that still use HEPA language.
The difference between H13's 99.97% efficiency and H11's 95% efficiency sounds small numerically but isn't: H11 lets through roughly 13 times more particles per cubic metre of air than H13. For someone with moderate to severe allergies or asthma, that gap translates into measurable symptom differences.
What HEPA Filters Actually Capture
Pollen: 10-100 microns — captured easily by any HEPA filter, including lower grades.
Dust mite allergen particles: 1-10 microns — captured by H13 and above effectively.
Pet dander: 0.5-10 microns — captured well by H13.
Mould spores: 2-10 microns — captured by H13.
Bacteria: 0.5-5 microns — H13 captures the majority.
Fine particulate matter (PM2.5): particles below 2.5 microns — H13 handles these, though at the smaller end of PM2.5 (0.1-0.3 microns) capture rates vary by product.
Viruses: 0.02-0.3 microns — HEPA alone captures some (those attached to larger carrier particles). Ionisation stages and UV-C claim additional virus reduction.
What HEPA doesn't capture: gases, VOCs, odours, nitrogen dioxide, ozone, carbon monoxide. These require activated carbon filtration. See our full explanation in how air purifiers work.
Three Purifiers with Genuine HEPA Credentials
Winix Zero S — H13 at 99.999%
The Winix Zero S quotes 99.999% particle removal efficiency — the five nines specification that implies H13 performance with margin. In independent tests of Winix products, the claimed filtration efficiency holds up. It covers rooms up to 100m² with a CADR of 410 m³/h and includes activated carbon for gases and odours alongside the HEPA layer.
For allergy sufferers who want a confirmed H13 filter without paying flagship prices, this is the value pick.
Philips Series 3000i — ECARF Certified
The Philips 3000i uses a NanoProtect HEPA filter and carries ECARF (European Centre for Allergy Research Foundation) certification — third-party independent testing of the product's effectiveness for allergy sufferers, not just the filter specification. That's a meaningful distinction: a certified product has been tested in-use, not just at the component level.
The 36-month filter lifespan is the other differentiator. Most H13 HEPA filters need replacing every six to twelve months. The Philips filter lasts three years, substantially reducing running costs.
Levoit Core 400S — H13 with Smart Sensor
The Core 400S uses an H13 HEPA filter and pairs it with a laser PM2.5 sensor. The sensor gives you real data on what the filter is capturing — useful for confirming that the purifier is actually responding to particle events in your home rather than running at a set speed indefinitely. CADR is 400 m³/h, covering up to 166m².
Filter Replacement: The Hidden Cost
A genuine H13 HEPA filter costs more to replace than a HEPA-type filter — roughly £25-45 for a branded replacement versus £10-15 for generic alternatives. However, genuine filters maintain their stated efficiency throughout their rated lifespan. Third-party replacements can be difficult to verify and may not meet H13 specification even if labelled as such.
If you buy a branded purifier, replace with branded filters. The purifier is only as good as what's in it.
Most manufacturers recommend filter replacement every six to twelve months depending on usage and air quality. Some units — like the Philips 3000i — include filter monitoring that tracks actual usage rather than a fixed countdown.
See our related guides: allergy air purifiers, air purifiers for asthma, and how air purifiers work. Or see the main air purifier roundup for full product recommendations.