Filter grades decoded
HEPA H13 vs H14 vs "HEPA-type", MERV ratings for DIY and ducted systems, and when carbon filters matter.
HEPA
“HEPA” means high-efficiency particulate air filter. The labels are defined by standards:
| Label | Standard | Minimum efficiency | Notes |
|---|---|---|---|
| E10–E12 | EN 1822 | 85%–99.5% | “EPA” grade, not HEPA |
| H13 | EN 1822 / ISO 29463 | 99.95% at the hardest-to-catch particle size | The common standard for good home purifiers |
| H14 | EN 1822 / ISO 29463 | 99.995% | Little extra benefit at home. Can mean more airflow resistance |
| True HEPA | US DOE | 99.97% at 0.3 µm | Comparable to H13 |
| “HEPA-type”, “HEPA-like”, “99% HEPA” | None | Unknown | Marketing terms |
Bigger isn’t always better: an H13 filter in a purifier with a strong fan beats an H14 in a weak one. The air delivered (CADR) matters more than going from H13 to H14.
MERV (for DIY filters and ducted systems)
MERV ratings (ASHRAE 52.2) are used for filters in central air systems, fresh-air units and DIY box-fan purifiers.
| MERV | Fine particles (0.3–1 µm) | Use |
|---|---|---|
| 8 | Low | Basic dust. Not enough for PM2.5 |
| 13 | ≥ 50% in a single pass, much higher for 1–3 µm | Minimum recommended for pollution and smoke |
| 14–16 | Higher | Better if the fan can handle the resistance |
A MERV 13 filter catches less per pass than HEPA, but a fan pushing a lot of air through a large MERV 13 filter can still clean a room fast. That’s how DIY box fans work.
Activated carbon
- Adsorbs some gases and odours (cooking smells, some VOCs). Does nothing for particles.
- A thin carbon-dusted sheet has very little capacity and saturates within weeks. Meaningful gas removal needs hundreds of grams to kilograms of granular carbon.
- For PM2.5 protection, carbon is optional. Don’t pay a premium for it unless odours or gases are a specific concern.
Pre-filters
A coarse mesh in front of the main filter catches hair and lint, protecting the HEPA layer. Clean it regularly as the manual says. It extends HEPA life, which matters in dusty Delhi.