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Air purifiers are only as good as the filter inside them — and that's where most of the confusion starts. "True HEPA," "HEPA-type," and "H13 medical grade" all get marketed like they're the same thing, and they really aren't. Add in the cost of OEM filters ($40–$80 apiece on some brands) vs generic replacements, and it's easy to either overpay or under-filter. The guides below break down filter grades, brand-specific replacement timing, warning signs, and whether third-party filters are actually safe to use.
New to air purifiers? Start with Why Air Purifier Filters Matter, then read True HEPA vs HEPA-type vs H13 so you actually know what you're buying.
All Air Purifier Filter Guides
Why Air Purifier Filters Matter
A purifier with a saturated or wrong-grade filter is just an expensive fan. Here's what the filter actually does and where most homeowners lose efficiency.
Read the guide →True HEPA vs HEPA-type vs H13
The marketing labels don't match the standards. Here's what each term actually certifies — and when "True HEPA" isn't true HEPA at all.
Read the guide →When to Replace by Brand
Dyson, Honeywell, Levoit, Coway, Blueair — each manufacturer has different replacement intervals and indicator logic. Here's a plain-English schedule by brand.
Read the guide →Warning Signs of a Failing Filter
Musty smell, louder fan, flashing lights, allergy flare-ups inside the house — the filter is often already past its useful life well before the indicator fires.
Read the guide →OEM vs Generic Replacement Filters
Third-party filters can cost 40–60% less — but are they safe for your purifier and your lungs? What to look for and what to avoid.
Read the guide →True HEPA captures 99.97% of 0.3-micron particles. H13 captures 99.95% of the 0.1–0.3 micron range — a different, tougher standard. If your purifier markets "HEPA-like" or "HEPA-type," it's neither, and the gap matters for allergies and smoke.
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