Views: 0 Author: Site Editor Publish Time: 2023-05-16 Origin: Site
Do you know the role air filters play in maintaining a clean and healthy environment? General air filters play a vital role in filtering particulates and suspended solids from gases, ensuring clean air in various applications such as clean rooms, laboratories, and HVAC systems. In this article, we will explore the different testing standards, classification methods and testing equipment used in the evaluation of general air filters. Knowing these important aspects will help you make an informed decision when choosing the right air filter for your specific needs.
Here is the content list:
Air filters for general ventilation are mainly used to filter particulate and various suspended matter from the gas. They are used in both air intake and exhaust applications. Air intake application is mainly clean rooms, clean plants, laboratories, HVAC systems and other occasions where clean air is needed. Exhaust application refer to certain production processes where there are particles and oil mist harmful to the environment or human body in the exhaust, air filters are needed to prevent environmental pollution, such as industrial boilers, cement plants, coke plants, etc.
Used in clean rooms, general ventilation filters are usually used as pre-filters in association with HEPA/ULPA filters. General ventilation filters are low cost, easy to replace, and filter most of the particulate matter when used in combination. This extends the life of the HEPA filter, reduces the frequency of cleanroom maintenance, and thus improves economic efficiency.
Currently, there are EN 779 Particulate air filters for general ventilation - Determination of the filtration performances in Europe, and ASHRAE 52.2 Method of testing general ventilation air-cleaning devices for removal efficiency by particle size in the USA. In order to put an end to the situation that the same products are classified differently and cannot be used universally due to different standards, the International Organization for Standardization (ISO) has issued ISO 16890 Air filters for general ventilation. ISO 16890 is being implemented worldwide and is in a "three-legged" stage with the two aforementioned standards.
General air filters have different classification test methods depending on the standards they are based on.
EN 779 test rig uses DEHS aerosol and ASHRAE 52.2 dust as the test aerosol. For coarse filters of class G1~G4, they are graded according to the average arrestance, and for medium filters of class M5~M6 and F7~F9, they are graded according to the initial efficiency and average efficiency @0.4μm. In addition, it is necessary to test the air volume vs. resistance, dust holding capacity, and arrestance as a function of dust load.
ASHRAE 52.2 test system uses KCl and dust as test aerosol, test the PSE of clean filter and after 5 dust load tests to derive the minimum PSE curve, which is used as the basis for MERV classification. It is also necessary to test the dust holding capacity, resistance as a function of air flow rate, and final resistance.
The test aerosol specified in ISO 16890 test system also combines the above two standards, using DEHS aerosol test 0.3 to 1.0 μm particle size and KCl aerosol test 1.0 to 10.0 μm particle size. The L2 dust of ISO 15957 was used in the dust load test. The ePM classification system was used and obtained by calculating the initial fractional efficiency and the fractional efficiency after discharged.
Different standards have different levels of classification, please see the following table:
Group | Class | Final test pressure drop | Average arrestance (Am) of synthetic dust % | Average efficiency (Em) of 0.4μm particles % | Minimum efficiency of 0.4μm particles % |
Coarse | G1 | 250 | 50≤Am＜65 | - | - |
G2 | 250 | 65≤Am＜80 | - | - | |
G3 | 250 | 80≤Am＜90 | - | - | |
G4 | 250 | 90≤Am | - | - | |
Medium | M5 | 450 | - | 40≤Em＜60 | - |
M6 | 450 | 60≤Em＜80 | - | ||
Fine | F7 | 450 | 80≤Em＜90 | 35 | |
F8 | 450 | 90≤Em＜95 | 55 | ||
F9 | 450 | 95≤Em | 70 | ||
Minimum efficiency is the lowest efficiency among the initial efficiency, discharged efficiency and the lowest efficiency throughout the loading procedure of the test. | |||||
MERV | Composite Average Particle Size Efficiency,% in Size Range, μm | |||
Range 1, 0.3 to 10 | Range 2, 1.0 to 3.0 | Range 3, 3.0 to 10.0 | Average Arrestance,% | |
1 | N/A | N/A | E3＜20 | Aavg＜65 |
2 | N/A | N/A | E3＜20 | 65≤Aavg |
3 | N/A | N/A | E3＜20 | 70≤Aavg |
4 | N/A | N/A | E3＜20 | 75≤Aavg |
5 | N/A | N/A | 20≤E3 | N/A |
6 | N/A | N/A | 35≤E3 | N/A |
7 | N/A | N/A | 50≤E3 | N/A |
8 | N/A | 20≤E2 | 70≤E3 | N/A |
9 | N/A | 35≤E2 | 75≤E3 | N/A |
10 | N/A | 50≤E2 | 80≤E3 | N/A |
11 | 20≤E1 | 65≤E2 | 85≤E3 | N/A |
12 | 35≤E1 | 80≤E2 | 90≤E3 | N/A |
13 | 50≤E1 | 85≤E2 | 90≤E3 | N/A |
14 | 75≤E1 | 90≤E2 | 95≤E3 | N/A |
15 | 85≤E1 | 90≤E2 | 95≤E3 | N/A |
16 | 95≤E1 | 95≤E2 | 95≤E3 | N/A |
Group designation | Requirement | Class reporting value | ||
ePM1,min | ePM2.5,min | ePM10 | ||
ISO Coarse | - | - | ＜50% | Initial grav. arrestance |
ISO ePM10 | - | - | ≥50% | ePM10 |
ISO ePM 2.5 | - | ≥50% | - | ePM 2.5 |
ISO ePM1 | ≥50% | - | - | ePM1 |
The most recognized general air filter testing equipment is ALF 114 General Air Filter Test System from TOPAS, Germany.
In addition, other countries, due to incomplete industry chain or high import tariffs, will adopt the way of processing air ducts in their own countries and buying particle counter, dust feeder, aerosol generator and other accessories to assemble. This way, due to the lack of various professional tests, such as counter and system self-cleaning, dust generation stability, concentration uniformity, etc., will lead to poor stability of the equipment and poor repeatability and accuracy of test results. Although the input is reduced, the role that the equipment can play is also discounted, and it may even happen that the product test is qualified, but the actual situation is not qualified.
China has a complete industrial chain in filter production, testing and cleanroom detection, from the sheet metal processing of the housing of the test rig, to the core components such as aerosol generator and particle counter, to the hardware and software for test action control. Relying on these advantages, Scince Purge Technology focuses on carrying out the development and manufacturing of filtration test equipment, and currently has SC-7099 series and SC-16890 test equipment for air filters for general ventilation.
SC-7099 FEH Air Filter Test System is less than 5 meters in length and there are 3 versions are available, basic version - with DEHS generator, advanced version - with dust feeding system, and superior version - with KCl generator and particle counter with 16 channels.
SC-16890 equipped with TSI oil aerosol generator, large particle KCl generator and 16-channels particle counter. And dust feeding system, test cabinet for filter discharge, fully meet the test requirements of ISO 16890.
General air filters are essential components in ensuring clean and pollutant-free air in various applications. By adhering to testing standards and utilizing appropriate test rigs, these filters are evaluated based on their efficiency, resistance, and filtration performance. Standards such as EN 779, ASHRAE 52.2, and ISO 16890 provide guidelines for classifying air filters based on their effectiveness in removing particles of different sizes. Additionally, reliable testing equipment like the SC-7099 and SC-16890 test equipment ensures accurate and repeatable test results. Understanding the classification and testing methods helps you to select the right air filters that meet your specific requirements for clean and healthy environments.
Interested in finding out more about quality air filters? Contact us. Scince Purge focuses on professional cleaning & filtration testing for over 20 years, we are always ready to help you.
