Why FFU filtration grade cannot be directly equivalent to ISO cleanliness grade
The two concepts are often confused
In clean room projects, we often hear this statement: using the FFU of H14 high-efficiency filter, the clean room can reach ISO level 5; using the U15 ultra-high-efficiency filter, it can reach ISO level 4. This statement directly corresponds to the filter grade and the clean room grade. It sounds simple, but it is not accurate.
Filter grade and ISO cleanliness grade are two different concepts with different evaluation objects. The filter rating describes how efficiently the filter itself filters particles of a specific size. ISO cleanliness levels describe the concentration of suspended particles in the air in a clean room or clean area. One is the equipment performance index, and the other is the regional environment index.
There is a relationship between the two, but they are not directly equivalent. Filters are an important means of controlling particles, but the final level of a clean room depends on the amount of dust generated, air supply volume, air flow organization, sealing integrity and operating status. Aili Industry has complete production capabilities in FFU complete machines and high-efficiency filters, and can provide configuration solutions according to the project's cleanliness goals. For the basic structure of the FFU machine, please refer toAili Industrial FFU fan filter unit。
What does the filter level describe?
Filter classes are usually classified according to EN 1822 or IEST standards. Codes such as H13, H14, U15, and U16 describe the filtration efficiency of the filter for the most easily penetrable particles. For example, the H14 filter has clear requirements for the filtration efficiency of 0.3 micron particles, and U15 and U16 have higher efficiency for smaller particles.
The filter rating is the result of leak detection and efficiency testing of the filter itself under standard testing conditions. It reflects the filtering capacity of the filter under test conditions and does not include the effects of installation sealing, box structure and room airflow.
The higher the filter grade, the stronger the ability to intercept particles, but this is not the only factor that determines the cleanroom grade.
What does ISO cleanliness level describe?
ISO cleanliness levels are classified according to the ISO 14644 standard, which describes the particle concentration per unit volume of air in a clean room. For example, ISO class 5 corresponds to the upper limit of the number of particles greater than or equal to 0.5 microns per cubic meter of air. The lower the ISO level, the lower the allowed particle concentration and the higher the cleanliness requirements.
The ISO cleanliness level is the result of sampling and counting according to standard methods under the actual operating conditions of the clean room. It reflects the actual particle level of the regional environment, which is affected by room dust, supply air, return air, personnel, equipment and operating status.
The same ISO level can be achieved in clean rooms with different areas, different air flow forms, and different operating conditions. The ISO grade is a regional indicator, not an equipment indicator.
Why can’t it correspond directly?
There are several main reasons why the filter grade cannot be directly corresponding to the ISO cleanliness grade.
First, the filter only removes particles in the air. It does not control dust generation in the room. If there are dust-generating equipment, personnel operations, or material handling in the room, the particle concentration in the room may still be high even if the air supply filter has a higher level.
Second, the installation of sealing affects the actual effect. If the filter passes the factory leak test, it does not mean that the seal is intact after installation. If the seal is not tight, unfiltered air may bypass the filter and enter the clean area, affecting the actual cleanliness.
Third, airflow organization affects particle distribution. Insufficient supply air coverage, poor return air, or airflow short circuit may lead to local particle accumulation. No matter how high the filter grade is, it cannot make up for the airflow organization defects.
Fourth, the operating status affects the results. The particle concentration is different in the empty state, static state and dynamic state. During dynamic operation, when personnel and process activity increase, particle concentrations may rise.
What other conditions does the cleanroom grade depend on?
The final level of the clean room depends on the cooperation of multiple conditions. The control of dust generation includes equipment exhaust, personnel operating regulations and material cleaning. The air supply volume needs to meet the air exchange frequency or air flow coverage requirements. Airflow organization needs to ensure that clean airflow covers key areas and brings polluted air to the return air outlet. Seal integrity includes filter mounting seals, ceiling seals, and envelope seals. Operation management includes the number of personnel, operating procedures and cleaning and maintenance.
Filter rating is one of the important criteria, but not the only one. When selecting the filter level, it should be determined comprehensively based on the amount of dust generated in the room, the air flow pattern and the target cleanliness level.
How to set filtering configuration correctly
Correctly setting the filtration configuration should start from the target cleanliness level, combined with room conditions and process requirements. First clarify the target ISO level and testing status. Reassess the amount of dust in the room and the sources of pollution. Then determine the air supply volume, airflow pattern and number of air changes. Then select the filter efficiency level and confirm the sealing method. Finally confirm the installation quality and operation management requirements.
For areas with high cleanliness levels, higher efficiency filters and good air flow organization are usually required. For areas with higher dust generation, increased source control or local exhaust may be required, rather than just higher filter ratings.
If the project requires filters of different efficiency levels, you can refer toHEPA and ULPA filters understand different grades of products from H13 to U17. For FFU matching filters, you can refer toFFU is equipped with ULPA ultra-high efficiency filter to understand the matching method of the whole machine.
Issues that should be confirmed in advance during project communication
In the clean room filtration configuration and grade confirmation stage, it is recommended to confirm the following with the FFU manufacturer and designer: target ISO cleanliness grade and testing status; room dust volume and pollution sources; air supply volume and airflow form; filter efficiency grade and sealing method; installation quality requirements; operation management requirements; detection methods and judgment standards; and explanation of the relationship between filter grade and cleanliness grade.
If you are planning a cleanroom FFU configuration, you can visitAili Industrial FFU fan filter unit to learn about the complete machine configuration, you can also contact Aili Industrial to obtain selection support based on the project's cleanliness goals.
in conclusion
The FFU filtration grade describes the filtration performance of the filter itself, and the ISO cleanliness grade describes the regional air particle concentration. The two evaluation objects are different and cannot be directly equated. Room cleanliness also depends on the amount of dust generated, air supply volume, airflow organization, sealing integrity and operating status.
Aili Industry has complete production capabilities in FFU complete machines and high-efficiency filters, and can provide configuration solutions according to the project's cleanliness goals. If you need to know more about the relationship between FFU filter configuration and cleanliness level, you can visitAili Industrial FFU fan filter unit , you are also welcome to contact Aili Industrial for project support.
