In the UK on the 30th of June 2018, the standard for testing air filter efficiencies changed from EN779 to ISO 16890. The old EN779 air filter grades, G1 to >95%, were replaced with the ISO 16890 system based on efficiencies at different particle sizes with the following ranges:
- ePM1 = 0.3 – 1μm
- ePM2.5 = 0.3 – 2.5μm
- ePM10 = 0.3 – 10.0μm
- ISO Coarse = Gravimetric filter arrestance for media unable to achieve 50% efficiency at ePM10.
The old EN779 standard was a measured percentage efficiency at 0.4μm particle size whereas the ISO 16890 classifications cover a broad range of particle sizes between 0.3 and 10μm
Why change to the new ISO 16890 classification?
The ISO 16890 classification system is the same system that the World Health Organization (WHO) uses in evaluating environmental air quality. Its lab test procedures more realistically simulate those of real-world performance whereas the EN779 system had unrealistic test conditions and test results with little real-world relevance.
Even though ISO 16890 has clear benefits as a classification system, many have been slow to take on the new system or haven’t. This may be partially due to its’ complicated nature, with many added classifications and percentages.
What does PM1 mean?
PM1 means a filter achieves at least a 50% efficiency of all Particulate Matter smaller than 1μm (but larger than 0.3μm).
- 1μm = 0.001mm
- 2.5μm = 0.0025mm
- 10μm = 0.01mm
What are the real-world applications of the ISO 16890 classifications?
Below are some examples of particles that are filtered in each category.
- ePM1 ≥50% = Viruses, most smoke, cooking oil, copier toner, most paint pigment & exhaust gases
- ePM2.5 ≥50% = Bacteria, fungal and mold spores,
- ePM10 ≥50% = Pollen and dust
- ISO Coarse ≥50% = Sand and hair
How does this affect filter ordering?
The change in classification systems means a name change for most products. An example is a G4 pleated panel is now an ISO Coarse 90% pleated panel and an 85%/F7 bag filter is now an ISO ePM1 65% bag filter. See the table below for a rough guide to conversions between the two systems.
Rather confusingly, a filter can fit into multiple categories because the range for each starts at 0.3μm. So, a filter can be ePM1 >65% and simultaneously ePM2.5 >80%.