HEPA Filters: Grades, Standards and the 'HEPA-Type' Trap

For a home purifier, H13 is the right target. H14 is not meaningfully better in a living room and usually costs more airflow, because denser media needs a stronger fan to push the same volume of air.

• The phrases 'HEPA-type', 'HEPA-like', 'HEPA-style' or 'HEPA-grade' — all mean it does not meet the standard.
• An efficiency claim at a convenient particle size, such as '99.9% at 1 micron'. Real HEPA ratings are quoted at the most-penetrating size, around 0.3 micron.
• No grade stated at all. A manufacturer that has an H13 filter says so, prominently.
• A washable 'HEPA' filter. Genuine pleated HEPA media is destroyed by water. If it is washable it is an electrostatic or mesh filter, which is a different and less efficient thing.
• A suspiciously low replacement-filter price. HEPA media is not cheap to make.

A filter rated H13 only delivers H13 performance if all the air actually goes through it. In practice many purifiers have gaps around the filter housing, and some fraction of airflow slips past the media entirely. The rating on the filter remains true; the rating of the machine does not.

Dyson is the main mainstream brand that certifies whole-machine sealing to HEPA H13 rather than just the filter, and it is a genuine engineering advantage. For other brands, look for phrases like 'fully sealed' and check that the filter seats against a gasket rather than simply resting in a tray.

• Rated life is typically 6–24 months. In Delhi, Ghaziabad or Noida, expect a third to a half of that.
• The reliable test is performance, not the calendar: if PM2.5 no longer falls quickly in a closed room, the filter is finished regardless of what the indicator says.
• Other signs: noticeably reduced airflow, the fan running at high speed constantly in auto mode, or a musty smell from the outlet.
• A filter can be exhausted before it looks dirty, and grey discolouration alone is not proof it needs changing.