air quality by reducing the concentration of particulate matter (PM).

To enable design engineers and

maintenance personnel to choose the correct fi lter types, international trade bodies and manufacturing companies want to see a well-defi ned, common method of testing and classifying air fi lters according to their particle effi ciencies, especially with respect to the removal of PM.

Regional standards apply testing and

classifi cation methods that do not allow any comparison with each other, and thus hinder global trade with common products. Additionally, the current industry standards have limitations in that they can generate results which often are far away from fi lter performance in service. A new ISO standard on air fi lters – ISO 16890: Air Filters for General Ventilation – off ers a new approach to fi lter classifi cation, which gives more meaningful results compared to the existing standards. ISO 16890 describes equipment, materials, technical specifi cations, requirements, qualifi cations and procedures to produce laboratory performance data. It also enables the designer to calculate an effi ciency classifi cation based on the measured fractional effi ciency which is converted into ‘particulate matter effi ciency’ (ePM). Published at the end of 2016, ISO 16890 represents the fi rst opportunity for global harmonization, replacing two existing standards – ASHRAE 52.2 in US and EN

779:2012 in Europe (both coexisting in Asia and the Middle East). There are important diff erences between ISO 16890 and the standards it replaces. In many aspects, the new test procedures are more demanding and this should lead to higher fi lter performance, better indoor air quality and greater health protection. The new test procedures are also more closely related to real-world fi lter performance and the classifi cation system is related to fi lter performance against three diff erent sizes of particles. Importantly, the smallest particle fraction of the three, so called PM1, represents the very fi ne particles that are known to be the most harmful to human health. Diff erent classes of PM are defi ned according to a particle size range, with the most important ones being PM10, PM2.5 and PM1. The US Environmental Protection Agency (EPA), the World Health Organization (WHO) and the European Union defi ne PM10 as particulate matter that “passes through a size-selective inlet with a 50% effi ciency cut-off at 10µm (10 microns) aerodynamic diameter”. PM2.5 and PM1 are similarly defi ned.

However, this defi nition is imprecise. Since an accurate defi nition of PM10, PM2.5 and PM1 is complex and diffi cult to measure, public authorities increasingly use a simplifi ed denotation of PM10 as being the particle size fraction less or equal to 10µm, PM2.5 less or equal to 2.5µm, and PM1 less or equal to 1µm.

Ending coughs, splutters and wheezes

Since January 2017, the new test standard ISO 16890: Air Filters for General Ventilation for fi lter testing and assessment replaced the previous standard, EN 779, and has sole validity from June 2018 onwards.

During the transitional period, both standards can exist in parallel. It is, however, possible for countries to withdraw the EN 779 standard with immediate eff ect. In this case, ISO 16890 replaces EN 779 transition-free. In future, fi lter effi ciencies will be determined with regard to the particulate classes PM1, PM2.5 and PM10. Based on these benchmarks, users will in future be able to more precisely select fi lters according to their individual requirements.

ISO 16890 comprises the following parts:

 Part 1: Technical specifi cations, requirements and classifi cation system based on particulate matter effi ciency (ePM)

 Part 2: Measurement of fractional effi ciency and air fl ow resistance

 Part 3: Determination of the gravimetric effi ciency and the air fl ow resistance versus the mass of test dust captured

 Part 4: Conditioning method to determine the minimum fractional test effi ciency

Part 1 of ISO 16890 establishes an effi ciency classifi cation system of air fi lters for general ventilation based on particulate matter (PM). It also provides an overview of the test procedures and specifi es general requirements for assessing and marking the fi lters, as well as for documenting the test results. ISO 16890 refers to particulate air fi lter elements for general ventilation having an ePM1 effi ciency less than or equal to 99% when tested according to the procedures defi ned within ISO 16890 1, ISO 16890 2, ISO 16890 3 and ISO 16890 4. Air fi lter elements with a higher initial effi ciency are evaluated by other applicable test methods.

July 2018 31

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