The new ISO 16890 standard has five different aspects:
1. Efficiency and pressure drop measurement
The efficiency test is broader than the test currently used under EN779: 2012 and AHSRAE 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 current standards is also calculated at only one particle size (0.4 µm), while the new ISO16890 focuses on various particle sizes from 0.3µ to 10µm. These changes will 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 also vary according to EN779: 2012 and ASHRAE 52.2. 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 degree both before and after discharge. This is very important as it most closely simulates normal operating conditions.
4. Dust holding and holding measurements
Compared to ASHRAE52.2 and EN779: 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 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.
Table1: Comparison Of IS016890, EN779:2012 And ASHRAE 52.2
|Filter test method||Efficiency measurement made using 0.4μm particles||Efficiency measurements made using 0.3-10μm particles. Classifications relate to results for E1, E2 & E3 efficiency classes - MERV rating||Efficiency measurements made using 0.3-10μm particles. Classifications relate to result 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|