Air filters for indoor environments: Interlaboratory evaluation of the new international filter testing standard ISO 16890

Electret filters are widely used in HVAC systems to decrease particulate matter in indoor environments. The previous standard in Europe for testing air filters for general ventilation was EN 779. In July 2018, it was replaced by the new international standard ISO 16890. One major change is the discharging process: It is now performed by treating the filters with saturated isopropyl alcohol (IPA) vapor. The process is intended to simulate a worst-case scenario of the filtration efficiency due to the reduction of the electret effect. These minimal efficiencies are a principal part of the filter classification. Therefore, two round robin tests with different filter classes (F9 and F7 according to EN 779) and up to eleven participants were carried out to evaluate the new test method by comparing the filtration efficiencies and pressure drops before and after the IPA treatment. Pressure drop measurements showed no mechanical altering of the material due to the discharging process. The calculated filter classes had a maximum deviation of 5%. Even with different equipment, the results indicate that the new ISO 16890 seems to be a viable test standard and a decent replacement for previous national standards.