The short version: HEPA captures a fraction more of the very smallest particles; MERV-13 captures the fine PM2.5 that drives health harm while letting a fan move far more air. For a home, throughput usually wins — cleaner air overall, at lower cost.
| MERV-13 | HEPA (H13) | |
|---|---|---|
| Captures PM2.5 | Yes (~93%+ typical) | Yes (99.95% at 0.3µm) |
| Airflow resistance | Low — high CADR | High — chokes airflow |
| Filter cost | Low, standard sizes | Higher, often proprietary |
| Best for | Whole-room clean air | Sealed medical/lab settings |
Ready to clean up your London air?
Luggable MERV-13 kits deliver up to 681 m³/h CADR — built on the Corsi-Rosenthal principle, from £229. Ships from Oxford in 2–3 days.
Shop the UK store → See all kitsWhy airflow wins at home
Clean-air delivery = filter efficiency × airflow. A HEPA unit that filters 99.95% but only moves 200 m³/h can be beaten by a MERV-13 kit moving 600 m³/h, because the MERV-13 kit simply processes far more of the room's air each hour. That's why the Corsi-Rosenthal box — pure MERV-13 airflow — punches so far above its price.
What the ratings actually mean
The two systems measure slightly different things, which is part of why the comparison gets muddled. MERV (Minimum Efficiency Reporting Value) is an American scale for how well a filter captures a range of particle sizes; MERV-13 sits near the top of what is practical for home airflow and captures roughly 93% of fine particles, including the PM2.5 fraction that matters most for health. HEPA is a pass-or-fail standard: a true H13 filter must capture 99.95% of particles at the hardest-to-catch 0.3 micron size. On paper HEPA wins that single-pass contest, and we won't pretend otherwise. The catch is that this higher capture comes from a denser media that resists airflow far more, so any fan pushing air through it moves less of it.
That is the honest trade-off, and it is why we frame everything around clean-air delivery rather than filter grade alone. A filter only cleans the air that actually passes through it. If a HEPA unit captures 99.95% but only pushes 200 m³/h, it can be comfortably out-cleaned by a MERV-13 kit moving 600 m³/h, because the kit simply processes three times as much of the room's air every hour. In a home, where air is constantly re-polluted by cooking, traffic ingress and daily life, that throughput is what keeps particle levels down.
Clean-air delivery is the number that matters
Clean-air delivery rate (CADR) is efficiency multiplied by airflow, and it is the metric independent testers use precisely because it captures both halves of the job. This is also why the Corsi-Rosenthal box — pure MERV-13 airflow with a huge filter surface area — punches so far above its price: it maximises throughput without choking on dense media. A pre-built kit applies the same logic in a quieter, tidier form.
- Choose MERV-13 for whole-room clean air at home, where airflow and low filter cost decide the outcome.
- Choose HEPA for sealed settings — labs, clean rooms, some clinical uses — where capturing the very smallest particles matters more than turning the room over quickly.
- Add activated carbon if odours, smoke or VOCs are the issue; neither MERV-13 nor HEPA particle media removes gases.
What this means for a UK home
For a typical London flat fighting traffic PM2.5 and seasonal pollen, MERV-13 airflow is the better-value answer nearly every time. You get cleaner air overall, cheaper standard filters and no proprietary lock-in. Ready to buy the media? See our MERV-13 filters page, or compare complete units in the best air purifiers for 2026.
Frequently asked questions
Is MERV-13 good enough for PM2.5?
Yes. MERV-13 captures the great majority of PM2.5, and because it allows high airflow it clears a whole room quickly — the metric that matters for home air.
When is HEPA actually better?
In sealed settings where you need to capture the very smallest particles at all costs and airflow is secondary — labs, clean rooms, some medical uses.