To meet indoor air quality needs for particulate matter filtration efficiency (ePMx) testing, the International Organization for Standardization has formulated the ISO 16890:2016 series of standards, which stipulates the testing methods and classification of ePMx.
In recent years, relevant research institutions and scholars have conducted various studies and discussions on indoor and outdoor air environments and the filtration efficiency of air filters on particulate matter mass.
Because multiple factors are involved and the main parameters are difficult to determine, using these research results to guide the design and selection of air filters is difficult.
After my research, Eurovent 4/23-2018 is a standard document supporting ISO 16890:2016. This standardization is simple, easy to implement, and has a high reference value. Therefore, I want to talk about how to choose air filters based on the ISO 16890 standard in conjunction with Eurovent 4/23-2018.
Eurovent4/23-2018 was formulated by the European Ventilation Association, affiliated with the European Industry Association, and was drafted by the European Ventilation Association’s Air Filter Product Group (PG-FIL, Product Group Air Filters). It was approved by the national member associations in Europe in 2018. The first edition was issued on January 9, 2016.
Impact of airborne particulate matter on society
Years of research have shown that the main components of suspended particulate matter (PM) in the air are sulfates, nitrates, ammonia, sodium chloride, carbon black, mineral dust, particles generated by combustion, etc. They are organic and inorganic, solid and liquid, mixed particles suspended in the air, and significantly impact the environment.
The social and economic losses caused by poor indoor air quality should be considerable.
Sources of indoor particulate matter
Eurovent4/23-2018 believes that the primary source of indoor particulate matter is the outdoor atmospheric environment. Most particulate matter in the outdoor air comes from various combustion sources in the local or surrounding areas. Especially in cities with heavy traffic and concentrated industrial areas, if the ventilation system does not adopt air filtration measures, the concentration of indoor particulate matter may exceed 90% of the outdoor concentration.
If solid and liquid fuels are burned indoors for cooking, heating, lighting, smoking, etc., they may be the second largest source of indoor air pollution.
The statistical shares of various factors that affect indoor air quality given in this standard are as follows:
- Outdoor air quality, 67.2%
- Indoor heating and other combustion equipment, 13.6%
- Water supply and drainage leakage, condensation, 10.4%
- Building foundation (soil in the soil) Radon), 8.0%
- Furniture, decorative materials, electrical appliances, etc., 0.3%
- Cleaning products and other household items, 0.3%
- Building materials, 0.2%
Suggestions for selecting air filters for ventilation systems according to ISO16890:2016 standards
When selecting air filters for general ventilation, the annual average mass concentration limits of ambient air particulate matter recommended by the Eurovent4/23-2018 are PM2.5, ≤10 μg/m3; PM10, ≤20 μg/m3; PM1 currently has no recommended value.
The standard points out that particulate matter will be generated and emitted into the air due to the specific daily activities of residents indoors. Therefore, the ventilation system must consider outdoor air quality and indoor pollution sources to achieve the desired indoor air quality.
Only by purifying the outdoor air to a level lower than the expected concentration of indoor particulate matter, only then can the indoor air be diluted to a concentration suitable for that location.
Recommended outdoor air levels and supply air levels
Considering that it is challenging to estimate indoor particulate matter, Eurovent 4/23-2018 gave a simplified air filter selection suggestion and believed that although this method is simple, it still considers all relevant factors. To maintain consistency with international standards, this method is based on the limits recommended by WHO.
This method divides outdoor air (ODA) into 3 categories
ODA1: The outdoor air is only briefly dusty, PM2.5≤10 μg/m3, PM10≤20 μg/m3
ODA2: Outdoor air contains high concentrations of particulate matter, PM2.5≤15 μg/m3, PM10≤30 μg/m3
ODA3: Outdoor air contains extremely high particulate matter concentrations, PM2.5>15 μg/m3, PM10>30μg/m3.
Like EN16798-3:2017, supply air (SUP) is divided into 5 levels. See table below
| Air supply | Concentration annual average PM2.5 μg/m3 | Concentration annual average PM10 μg/m3 |
| SUP1 | ≤2.5 | ≤5 |
| SUP2 | ≤5.0 | ≤10 |
| SUP3 | ≤7.5 | ≤15 |
| SUP4 | ≤10.0 | ≤20 |
| SUP5 | ≤15.0 | ≤30 |
Recommended minimum filtration efficiency of air filters for different ventilation systems
According to different ventilation systems and outdoor environment categories, Eurovent 4/23-2018 recommends the minimum particle filtration efficiency of air filters configured in the ventilation system under various combinations. See below table:
| Out Door Air | SUP1 ePM1 | SUP2 ePM1 | SUP3 ePM2.5 | SUP4 ePM10 | SUP5 ePM10 |
| ODA1 | 70 | 50 | 50 | 50 | 50 |
| ODA2 | 80 | 70 | 70 | 80 | 50 |
| ODA3 | 90 | 80 | 80 | 90 | 80 |
The purpose of installing air filters in the air conditioning and ventilation system is not only to prevent indoor air pollution and improve air quality but also to prevent various heat exchange, humidification, and other equipment in the air conditioning and ventilation system from reducing the efficiency or being damaged due to dust accumulation.
Therefore, it is advisable to configure a pre-filter with ePM10 that is at least 50% at the fresh air inlet.
Pay attention to air filter resistance
I want to point out that while the air filter meets the particle filtration efficiency, more attention should be paid to its flow resistance. Under the general situation of energy conservation and emission reduction, the requirements for consumption reduction of air conditioning and ventilation systems are constantly increasing. The flow resistance of the air filter is often the main component of the total pressure drop in the mechanical ventilation system, which significantly impacts the total energy consumption of the system operation.
Comparison of ISO 16890:2016 and EN 779:2012 air filter classification
As I know, in the EN 779:2012 standard, air filters of all levels above medium efficiency and below high efficiency are classified according to their counting filtration efficiency value for artificial experimental aerosol 0.4μm particle size barrier, while ISO 16890: 2016 is classified according to the mass filtration efficiency of air filters for different particle groups of artificial experimental aerosols (i.e., ePM1, ePM2.5, ePM10).
Because these two standards have substantial differences in classification definition methods and experimental data processing, their filtration efficiency values cannot be directly compared, and there is no method of mutual conversion.
EN779 and ISO 16890 efficiency grade conversion
To compare the test values of these two different filtration efficiencies of the same air filter and facilitate the reference when selecting air filters during the replacement stages of these two standards, the same test was carried out under the auspices of Eurovent Certita Certification—the comparative experiment of air filter methods specified in two standards.
Air filter manufacturers, which account for about 70% of the European market share, participate in this activity.
The resulting numerical comparison table is as follows:
| EN779 | ISO16890 ePM1 Average efficiency range % | ISO16890 ePM2.5 Average efficiency range % | ISO16890 ePM10 Average efficiency range % |
| M5 | 5-35 | 10-45 | 40-70 |
| M6 | 10-40 | 20-50 | 60-80 |
| F7 | 40-65 | 65-75 | 80-90 |
| F8 | 65-90 | 75-95 | 90-100 |
| F9 | 80-90 | 85-95 | 90-100 |
Inspiration from Eurovent 4/23-2018
I believe that this standard is the product of the cooperation of many air filtration experts and manufacturers in EU countries. It summarizes many years of practical experience in the European air conditioning and ventilation industry. The conclusions expressed in it are realistic and confident.
Eurovent 4/23-2018 is a good way to help the purification industry in some countries get out of the current dilemma in air filter selection and design in controlling indoor particulate matter concentration.
Dilemmas currently faced in air filter selection and design
When calculating indoor pollution sources, it is necessary to determine the penetration coefficient of outdoor particulate matter and the amount of outdoor air leakage based on the correlation between indoor and outdoor particle concentrations measured from actual measurements.
The determination of these values is quite complex. Different building structures are different. Rooms in the same building with different orientations and floor heights have different wind and thermal pressures due to changes in wind direction, wind force, and temperature differences between inside and outside. It is difficult to determine the penetration coefficient and leakage air volume.
In this case, before a “more stringent and practical” method is developed, we can learn from the path of Eurovent 4/23-2018 and explore design guidelines suitable for controlling indoor particulate matter concentration to ensure air quality.
Last conclusion
Considering the current situation of the atmospheric environment in each country, the layout method and operating system of the air conditioning and ventilation system, etc., combined with Eurovent 4/23-2018, it is more appropriate to research an air filter selection method suitable for this region. Undoubtedly, Eurovent 4/23-2018 has excellent reference and guidance significance.
