So why a new standard? There are many reasons. One is to move away from the use of the ASHRAE test dust to SAE ISO fine test dust which will be a blessing for many. The other is an attempt to have a different challenge aerosol particle size than the DEHS 0.4 microns currently used.
The jury is very much still out on the details of this proposal but the concept currently on the table appears to move away from 0.4 micron DEHS efficiency of EN779 to larger PM1 (Thanks Thomas for letting me know), PM 2.5 and PM10. PM2.5 is an industry standard for measuring pollution in the atmosphere and the efficiency of filters to capture these is seen as important. However 0.4 micron particle size is in the area where soot particles are more likely to be found and these are considered more damaging in terms of health.
Furthermore PM 2.5 and larger particle sizes are less likely to be affected by static discharge from the IPA soak making ratings based on this less likely to be significantly affected due to the discharge test as the efficiency of such particles is much more mechanical rather than diffusion based.
The final version of this standard is still some time away but expect to hear much more about it in the near future.
14th September:
As an addendum to this discussion, I posted this onto LinkedIn and the following update was given to be by R Vijayakumar, Founder and Chairman of Aerfil in the US and who sits on the US ISO standards committee:
"I believe it is out for DIS registration which is the first step in the process. Also, I believe the proposed standard is meant to take into account the weaknesses, e.g., dust, and strengths of the EN and ASHRAE standards. There is on going debate, at least within the US and a few other countries on the merits of some of the new techniques proposed, so it not yet a done deal for all the members of the committee. For example, from the discussions we have had within the US TAG, there is quite a bit of opposition to the PM classifications as proposed since the use of PM will not be in line with the US regulatory specifications. So I am not sure how the US will vote on this standard. I have heard that other countries have also some reservations."
10th November:
Having spoken in detail about the ISO16890 proposal with the German representative on the TC142 committee, I have a much clearer picture of the plan.
"0.4µm for most applications has no relevance at all and the behaviour of air filters to ASHRAE dust loading is completely different to what we experience under real-life conditions.For most of the fine filters when operated with ambient air, the efficiency does not increase, in fact it does decrease for all of them including filters made of micro glass papers. With the new approach, we cummulatively calculate the efficiency to PM1, PM2.5 and PM10 dust fraction, each time for the whole size range 0.3 to 1µm, or 2.5 µm or 10µm, respectively.
With this, filters are grouped accordingly, a filter with a PM10 efficiency >50% is called PM10-filter, a one with >50% for PM2.5 is called PM2.5 filter and so on. In the current draft there will be no further classification. Labelling will be ISO PM10 60% or ISO PM1 90% (always rounded to full 5% steps). With this, you get to a quite nice differentiation of the air filters as an M6 will have around 60% PM10 and an F9 around 90 or 95% PM1.
All measured in initial state without dust
loading."
Having tested the hypothesis myself based on a F9 filter element using the PM1 and PM2.5 data, I can confirm the performance would reach F9 based on an initial 96% efficiency (by KCl) at PM1 by this methodology.
The next few months should be interesting.
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