This distinction matters more than it might seem, and it’s worth checking the exact wording on any purifier’s listing.
What “True HEPA” specifically means
True HEPA is a defined, standardized claim — commonly 99.97% capture of particles at 0.3 micron. Xiaomi states this explicitly for the Smart Air Purifier 4 Compact, which is a real, checkable specification.
“HEPA-style” or “HEPA-like” isn’t the same claim
These terms describe a filter inspired by or similar to HEPA design, without meeting the actual defined standard. They’re not inherently useless, but they carry no equivalent guarantee — check for the specific “True HEPA” wording and an actual percentage if the filtration standard matters to your decision.
Particle size changes what a percentage means
Dyson states 99.95% removal at 0.1 micron for the Purifier Cool PC1 — a smaller particle size than the 0.3 micron standard True HEPA claims typically use. A high percentage at a smaller particle size is a genuinely strong claim, but it isn’t directly comparable to a True HEPA percentage without accounting for that difference.
Look for the testing standard, where stated
Dyson also cites testing to EN 1822, a recognized European standard for filtration testing — a detail worth looking for on any purifier claiming a specific capture percentage, since it indicates the claim was tested against a defined method rather than simply asserted.
What we would not do
Treat any unqualified “HEPA” claim as automatically equivalent to True HEPA. Read the specific wording and, where available, the tested particle size and standard before assuming two purifiers’ filtration claims mean the same thing.
Check your own manual before you follow anything here. Humidity ranges, wattages, voltage and current ratings differ from model to model, and the manufacturer's figures take precedence over anything written on this site. We report what makers and monitors publish — a target humidity percentage, a heater's tip-over and overheat protection, a plug or thermostat's maximum load rating — and we never turn a reading into a health verdict or a diagnosis. Questions about air quality and health are matters for a qualified professional and your national health authority, and this site points you to them rather than restating them. Where wiring, voltage or load ratings are involved, matching them exactly to your appliance is a safety matter, not a technicality.
The questions that keep coming up
Does a higher percentage always mean a better filter?
It's one real factor, but check the particle size it's measured at too — Dyson states 99.95% at 0.1 micron, a smaller and generally harder-to-capture particle size than the 0.3 micron commonly used for the 99.97% True HEPA standard, so the two aren't directly comparable on the percentage alone.
Last reviewed 24 August 2026