An introduction to filter classifications using the ISO 16890 standard
Standards Australia is in the process of replacing the AS1324 filter series, with the replacement of the existing G1-G4 and F5 - F9 filter classifications with the ISO 16890 series (Figure 1). While at first glace, the new filter classification method appears far more complicated to apply, the new rating system is an improvement as it better reflects the actual filter performance and will help to ensure adequate protection from airborne particulates for occupants of health facilities. The adoption of the ISO 16890 series does not affect the Australian HEPA filter standard (AS4260) used to filter air for surgeries and areas in the hospital with immunocompromised patients.
Figure 1 - AS1324 is being replaced by ISO/AS16890 (Source Table 5.1, DA15, AIRAH guide to Air Filters and Cleaning Devices)
Understanding particle size
The rationale behind the new filter classification method is to better/more accurately define the particulates arrested by the filter. The old classification scheme, while simple, would give no estimate of particulate arrestance, and users would need to look up the standard to try to understand how effective these filters are. There is nothing intrinsically informative about an F5 filter vs an F9 filter and what a user could expect in terms of cleaning air.
The new filter classification method describes the particulate arrestance of the filter that is specified. An ISOePM2.5 65% has been tested to remove 65% of PM2.5 particulates (ie particles smaller than 2.5 microns). The same filter will remove a higher proportion of PM10 particulates but a lower proportion of PM1 particulates. The selection of this particulate size range by ISO 16890 is deliberate since these smaller “respirable particles” (10µm or smaller) embed deep in the lungs.
Exposure to PM2.5 particulates has been linked to heart disease, stroke, lung cancer, chronic lung disease, and respiratory infections.[1] Figure 2 shows how particulate penetration in the lung varies based on particle size.
Figure 2 - Particulate penetration in the human lung (Source: TBH Company Catalogue)
The soon to be published ISO/AS 16890 classification method challenges a filter with 12 different particle sizes in the 0.3µm to 10µm size range. For reference, a fine human hair is between 50 – 70µm in size while respirable dust is generally so small to be invisible to the naked eye (Figure 3). The smallest particle tested (0.3µm) is in the pathogen size range and typical of the size of many smaller bacteria while the largest particle (10 µm) is typical of smaller dust particles, pollen and mould.
Figure 3 - Particle sizes in the micron range (Source: US EPA)
How the new classification scheme works
For a filter to be classified in accordance with the ISO 16890 method, it needs to capture at least 50% of one of the three main particulate classes: ePM1, ePM2.5 or ePM10. The “e” denotes the efficiency of the filter to that size category of particle. The ISO/AS 16890 standard will also have a fourth category called ‘Course filters’ for these filters which do not meet a minimum ePM10 arrestance of 50%. For example, if a tested filter only captures 40% of the ePM10 particles, then it can be classified as a “PM Coarse 45%” filter. Course filters are not recommended for most HVAC applications.
Figure 4 seeks to give a visual representation of this filter classification method. Once a filter has achieved the 50% arrestance threshold in that particulate category, it will be specifically classified in terms of its % arrestance of the particle size range (ie ePM1, ePM2.5 or ePM10). This is denoted as a % arrestance in 5% increments – for example “ePM1 55%”.
Figure 4 - Visual representation of general filter categories
The application of the correct ISO filter classification based on particle arrestance is illustrated in Figure 5. Following testing, these commercially available filters achieved the following % arrestance for the particulate sizes ePM1, ePM2.5 and ePM10. The final ISO 16890 classification is expressed as a % of the finest particulate captured at an arrestance rate of >50%. For example, a filter capturing 71% ePM1 will be classified as a “ePM1 70%” filter. Three other examples highlighted in the figure are described below:
· The DriPak SX M6 is classified as an ePM10 65% and arrests 65% of the ePM10 particles but a lower percentage of the ePM2.5 and ePM1.
· The DuraVee DVHXL95 is classified as an ePM1 70% and arrests 71% of the ePM1 particles and a higher percentage of the ePM2.5 and ePM10.
· The HydroVee HV95 is classified as an ePM1 50% and arrests 54% of the ePM1 particles and a higher percentage of the ePM2.5 and ePM10.
Figure 5 – Selection of the correct ISO classification for a filter performance (Source: AAF 2018).
An example of a typical filter label applying the ISO 16890 classification is show in Figure 6. This filter installed in an air handler, is an ePM2.5 70% filter. This grade of filter is typically used in commercial offices in urban areas.
Figure 6 – Example of a filter label applying the ISO16890 classification
Choosing the right filter for your HVAC system
Selection of the right filter for the HVAC systems in your hospital depends on the specific requirements for the facility and the quality of the outdoor air where you are located. This topic will be tackled in a future Healthcare Engineering articles, however some excellent on-line guidance is available in the following publications:
Eurovent 4/23 – 2022 Selection of EN ISO 16890 rated air filter classes for general ventilation applications. Fourth Edition
The Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH) publication Design Application Manual 15 - Air Filters and Cleaning Devices – Selection and Application
The transition to the ISO 16890 standard will occur over a 2-year period commencing from mid-2024 with the publication of the AS/ISO edition of the standard by Australian Standards. Until then, the AS1324 filters classification will continue to be used by commercial suppliers as we transition to the new system. Hospital engineers and their mechanical contractors should become familiar with the new ISO classification scheme as filter manufacturers and suppliers transition to the new standard.
For further training and details please join us for our Lunch + Learn Professional Development Session On Weds April 10.
Author: Gregor Riese, Director, Opira Group
Disclosures: Opira is an Australian-based supplier of filtration, UV and disinfection technologies servicing the healthcare and pharmaceutical sectors. This article was written by a human being. The author can be contacted at gregor@opira.com.au