Air filter classification according to ISO 16890

Air filter classification according to ISO 16890


ISO 16890 provides determination procedures that more realistically simulate actual operating conditions, replacing the G1 – F9 filter classification of old standards with a PM1, PM2.5 and PM10 particle classification system.

The effects of particulate matter (PM) on human health have been extensively studied and the results are that fine dust can be a serious health risk, contribute to or even cause respiratory and cardiovascular disease.

A glass particle is described in the context of ISO 16890 as the proportion of the size of natural aerosols (liquid and solid particles) suspended in ambient air.

The ePMx symbol describes the efficiency of an air purifier on particles with an optical diameter between 0.3 μm and x μm.

Unlike EN 779, which defines filter classes, ISO 16890 is classified by filter group, evaluating filter performance by stopping particle sizes of 0.3 to 10 μm.

The difference is, therefore, that the old standard test stops only one particle size (0.4 μm), while the new standard specifies a stop over a spectrum of particle sizes.


The new ISO16890 standard divides air filters into four groups. A prerequisite for each group is that the filter captures at least 50% of the appropriate particle size range. If a filter, for example, stops more than 50% of PM1 particles, it will be grouped as an ISO ePM1 filter. Appropriate efficiency is then shown, rounded off in 5% increments.

In addition to fine dust filters, the new ISO standard also evaluates coarse dust filters as ISO COARSE (filters) that capture less than 50% of PM10.

An air filter qualifies for the ISO ePM1 or ISO ePM2.5 group if it achieves a minimum efficiency of 50% or more for particle sizes ≤1 μm or ≤2.5 μm.

In addition to achieving a filter group, the complete ISO 16890 classification also includes average filter performance.

Minimum efficiency is defined as the efficiency achieved after electrostatic discharge of the filter before testing. The average efficiency is calculated by the average efficiency of the filter in the untreated state, ie before discharge and in the empty state.



If a filter achieves a minimum efficiency of 45% in the PM1 size spectrum and 56% in the PM2.5 size spectrum, it does not qualify for the ISO ePM1 filter group – which is missed by 5% – but qualifies for the ISO ePM2.5 filter group. Assuming the average efficiency of this filter for ISO ePM2.5 particles was 68%, this percentage is rounded to the nearest increment of 5% (rounded to 65%), and the ISO 16890 filter classification is therefore ISO ePM2.5 65%.

For classification in the ISO filter group, the ePM10 must achieve an average ePM10 efficiency of ≥ 50%. Filters with an average efficiency <50% for this range of particle sizes are classified into the ISO coarse filter group and according to the initial gravimetric deadlock.

Table 1. Filter classification by particle size

Filter Particle size (μm) Sorting criterion Example
ISO ePM1 0.3 ≤ x ≤ 1 Minimum efficiency ≥ 50% Viruses, nano particles, exhaust gases…
ISO ePM2,5 0.3 ≤ x ≤ 2,5 Minimum efficiency ≥ 50% Bacteria, pollen, toner dust, mold spores…
ISO ePM10 0.3 ≤ x ≤ 10 Average efficiency ≥ 50% Pollen, sand dust…
ISO Coarse 0.3 ≤ x ≤ 10 Average efficiency <50% Sand, hair…


For ease of understanding and selecting the right filter, the table below shows a comparison of EN779 and ISO 16890.

  EN 779 ISO 16890
Name: Air particulate filters for general filtration Filtri za zrak za opću ventilaciju
Validity: Until the middle of 2018. year From the end of 2016. year
Stop estimation: Filter class G1 to G4: average gravimetric stops.

Filter class M5 to F9: stopping particles up to 0.4μm in diameter.

The classification is based on the stopping of particles in the range of 0.3 – 10 μm in diameter.


Filter classification: Filter classes:

G1 – G4

M5 – M6

F7 – F9

Filter groups:

ISO Coarse


ISO ePM2,5


Essential characteristics: –   Gravimetric stop average

–   Average efficiency and minimum efficiency for particles with a diameter of 0.4 μm

–   Dust retention capacity for test particles

–   Pressure drop as a function of volumetric flow rate


–   Gravimetric initial stop (mandatory for ISO Coarse only)

–   Average fractional stop for PM1, PM2.5, and PM10

–   Minimum efficiency ≥50% for the PM group tested

–   Dust holding capacity for test dust

–   Pressure drop as a function of volumetric permeability