ISO 16890 vs EN 779 and ASHRAE 52.2

The ISO 16890 standard differs from EN 779:2012 and ASHRAE 52.2 in five aspects.

1. Efficiency and pressure drop measurement

The efficiency test is broader than the test currently used under EN 779:2012 and ASHRAE 52.2, covering a range of particles from 0.3 µm to 10 µm, whereas the previous test only ranged from 0.3 µm to 3 µm. Extraction efficiency in the older standards is also calculated at only one particle size (0.4 µm), while ISO 16890 focuses on various particle sizes from 0.3 µm to 10 µm. These changes provide a more accurate classification of air filters in terms of particle sizes and their effects on the indoor environment.

2. Discharge conditions

Discharge conditions vary between the standards. The isopropanol method was chosen for the filter discharge efficiency test in accordance with ISO 16890 because of its good discharge properties. Although the new test method is slower and more complicated to run in the laboratory compared to previous wet processes, it empties the filter 100% without affecting the fiber structure of the filter and provides more accurate test results.

3. Post-discharge efficiency measurement

This measurement evaluates the functionality of the air filters after use. The efficiency of the post-discharge filters should be similar to the first efficiency classification to obtain the respective classification grade. In other words, an ePM1 filter that provides 60% efficiency against PM1 should reach this 60% efficiency both before and after discharge. This closely simulates normal operating conditions.

4. Dust holding and loading measurements

Compared to ASHRAE 52.2 and EN 779:2012, the test dust in ISO 16890 has been converted into a finer test dust specified as L2 under ISO 15957. This finer powder takes longer to load in the lab, but better simulates real-life conditions.

5. Calculation and ePM classification

Major differences between the previous standards and ISO 16890 emerge in the final classification and calculation step. By calculation, the measured test results are converted and correlated with known outdoor air pollution measurements PM1, PM2.5 and PM10.

Comparison table

	EN 779:2012	ASHRAE 52.2	ISO 16890
Filter test method	Efficiency measurement made using 0.4 µm particles	Efficiency measurements made using 0.3-10 µm particles. Classifications relate to results for E1, E2 and E3 efficiency classes (MERV rating)	Efficiency measurements made using 0.3-10 µm particles. Classifications relate to results for PM1
Discharging method	Discharge only filter media, using IPA soak. A tough discharging method.	Discharge entire filter using KCl salt. A soft discharging method. Discharge is not mandatory; may be applied as Appendix J procedure.	Discharge entire filter using IPA vapor. A tough discharging method.
Filter loading method	Dust loading with ISO fine dust. Fine dust (more like real-world).	Dust loading with ASHRAE dust. Coarse dust.	Dust loading with ASHRAE dust. Coarse dust.
Classification system	9 classes	16 classes	49 classes in 4 different groups

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