Air filters play an important role in a heating, ventilation and air-conditioning (HVAC) system to maintain good indoor air quality of a building. The air filter test standards act as a guideline to evaluate the air filter performance. The current global test standard, ISO 16890:2016 adopts particulate matter classification which can be easily understood. The European standard, EN 779:2012 is obsolete and replaced by ISO 16890:2016 in June 2018. ASHRAE 52.2:2017 which adopts the minimum efficiency reporting value (MERV) classification is still widely used in the United States. Some countries in Southeast Asia such as Malaysia, Brunei and Singapore are applying different standards: EN779, ASHRAE 52.2 and ISO 16890. A standardization of the air filter testing and classification is undoubtedly important in the global air filtration market. This paper can act as a reference and assist these developing countries in adopting the suitable air filter testing standard to develop their national standard. As all three standards have no specifications on energy efficiency classification, the energy rating system can be obtained using Eurovent 4/21-2018. The HVAC-system-supplied air quality can be further improved with the consideration of WHO annual mean pollutant limits and EN 16798-3 air classification to determine the supply air cleanliness. Practical application: Although EN 779 is replaced by ISO 16890, some developing countries are still in the transition period. Manufacturers and consumers apply different standards which are EN 779, ASHRAE 52.2 and ISO 16890; therefore, a global filter testing standardization is important. This paper can act as a reference and assist the countries in other regions especially in Southeast Asia to develop respective national standard. Besides, some recommendations are given to improve the air filtration and ventilation system by referring to the WHO guidelines for the air pollutant limits, EN 16798-3 for the supply air quality and Eurovent 4/21 for the air filter energy rating.

Fibrous filter media is typically pleated to increase effective filtration area, but the pleat geometry could influence the filtration performance. The previous work focused on the pleat geometry numerically and mainly limited to the cartridge filters with small pleats while the study on the heating, ventilation and air-conditioning (HVAC) filters is limited. In this study, a full-size pleated fibrous air filter was used to investigate the effect of pleat geometry on the filtration performance experimentally with reference to the air filter test standard, ISO 16890. The pleat geometry was found to have an insignificant effect on the filtration efficiency. The optimum pleat ratios are 13.08–14.57 for minimum initial pressure differential and 9.96–11.75 for optimal specific resistance coefficient of dust cake, [Formula: see text]. The overall optimum pleat ratio range is 13.08–14.57 to obtain an optimal filtration performance at low initial pressure differential and low [Formula: see text] while attaining a high dust holding capacity. The findings of current work were obtained by a comprehensive study on the filtration performance including the clean and dust-loaded states of the HVAC filters, at the actual operating velocity and could be directly applied in the actual filter depth selection based on the AHU’s space limitation.

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Filtration velocity is a fundamental parameter that influences fibrous filtration performance. The previous work focuses on the effect of velocity on filtration performance, mainly using downsized filters, a flat sheet media or numerical methods. In this study, the actual performance of the full-sized fibrous filters was simulated according to standard test procedures, ISO 16890:2016 at different filtration velocities. The experimental findings show that the filtration efficiency increases with increasing velocity as the inertial impaction increases at higher velocity. The initial pressure differential shows an increasing relationship at [Formula: see text] with increasing velocity. The dust cake specific resistance coefficient, K c increases linearly with the velocity at the depth filtration stage and the beginning of transitional filtration stage. K c exhibits a quadratic growth with filtration velocity since the middle stage of transitional filtration and surface filtration. Dust holding capacity would be reduced and the final pressure differential would be increased with the increasing velocity due to the greater force incurred by the higher velocity, causing the filter media to deform and rupture easily. The experimental outcome of this study can be applied directly to industrial and commercial heating, ventilation and air conditioning design in consideration of the filter pressure differential for a lower energy consumption without compromising the efficiency for indoor air quality.