There are three main rating systems to know. ISO 16890 rates general ventilation filters as ePM1, ePM2.5, ePM10 or Coarse. EN 1822 and ISO 29463 cover higher-efficiency filters, including H13 and H14. ISO 29461-1 rates gas turbine filters from T5 to T13. MERV is a separate US scale, with no official conversion to the others.
How does ISO 16890 classify ventilation filters?
ISO 16890 groups filters by how well they capture particles of different sizes. It replaced EN 779, the older F7 and M5 style ratings. Results are reported in 5% steps, so a filter that tests at 57% is reported as 55%.
| Group | Requirement | Typical use |
|---|---|---|
| ISO ePM1 | ePM1,min ≥ 50% | Final filters in offices, hotels and food production |
| ISO ePM2.5 | ePM2.5,min ≥ 50% | Commercial buildings and pre-filters for HEPA |
| ISO ePM10 | ePM10 ≥ 50% | First stages and less sensitive spaces |
| ISO Coarse | ePM10 < 50% | Pre-filters that catch larger dust |
What do E, H and U classes mean?
For higher efficiency, EN 1822 defines EPA (E10 to E12), HEPA (H13 and H14) and ULPA (U15 to U17) classes, tested at the most penetrating particle size. ISO 29463 is the related international standard. An H13 captures at least 99.95% and an H14 at least 99.995%. Read more on our HEPA filters page.
What about gas turbine filter classes?
ISO 29461-1 classifies turbomachinery inlet filters from T5 to T13, using ISO 16890 tests for the lower classes and ISO 29463 tests for T10 and above. The full table is on our gas turbine filters page.
Can you convert between MERV, F7 and ePM ratings?
Not exactly. MERV comes from the US ASHRAE 52.2 standard, F7 comes from the withdrawn EN 779, and ePM comes from ISO 16890. They use different test methods, and Camfil notes there is no direct comparison between the classes. Conversion charts are only rough guides, so ask for a test report in the standard you are specifying.
Which class should you choose?
- Start from the risk
People’s health, a product, a process or a machine.
- Build in stages
A coarser filter protects a finer one and makes it last longer.
- Check your fan
Higher classes generally add resistance. Confirm that your system can deliver the required airflow.
- Compare lifetime cost
Include energy and change-outs, not only the price of the filter.