Can FFU independently determine the cleanroom grade?

FFU is the air supply terminal in the clean system. It can provide filtered air, but it cannot alone determine the cleanliness level of a room or area. The site level also depends on the pollution load, enclosure sealing, air supply and return organization, personnel and material activities and operating status. It is a common misunderstanding in selection and acceptance to directly regard FFU parameters as room grade certification.

The following will start from the aspects of equipment capabilities, system conditions, and on-site verification.

First distinguish between equipment parameters and site levels

The FFU's filtration level, air volume, and external static pressure describe the equipment's capabilities under specific test configurations. Cleanroom classes describe the concentration of air particles in a specified area, specified particle size and occupancy conditions. The two are related, but not the same concept.

If you are still unclear about the difference between space rating and filter efficiency, you can read What is the difference between cleanliness level and filtration efficiency ? Let’s first clarify this basic concept. The cleanliness level must indicate the particle size and state. For specific reasons, please refer to Why must the particle size be indicated in the cleanliness grade?。

FFU parameters describe device capabilities but cannot replace the system

Filtration level, air volume and static pressure describe different performances respectively. When purchasing, you should check the working point and sealing method after assembly. The filter efficiency or the air outlet surface reading cannot be directly used as proof of the whole room grade.

For example, an FFU has a high nominal air volume, but after being installed in the ceiling and connected to a long air duct or a high-resistance filter, the actual operating point may be significantly reduced. At this time, you need to view the complete performance curve. For specific methods, please refer to Why should we look at the complete performance curve when selecting FFU? . If you only look at the maximum air volume or maximum pressure, it is easy to misjudge the on-site capacity.

Similarly, whether the FFU nominal air volume includes the filter load should also be based on the model data and test conditions. For relevant judgments, please refer to Is FFU's nominal air volume tested with a filter?。

The room system determines whether abilities can be exerted

FFU provides filtered air supply, but the room system determines whether this air can protect critical areas. Poor return air, intensive personnel activities, input of pollution at the door, and unsealed enclosures may all cause local particles to rise.

If the return air path is blocked by equipment or shelves, the airflow may be short-circuited and the total air volume may appear to be sufficient, but the workstation protection will be insufficient. At this time, it is necessary to check the airflow path and return air layout instead of continuing to increase the number of FFU. For on-site performance with insufficient number of FFU, please refer to What are the on-site manifestations of insufficient FFU quantity?。

Containment sealing is also critical. If gaps in doors and windows, ceiling openings, and pipe penetrations are not sealed, background air will continue to enter. Please refer to the applicable boundaries for installing FFU in ordinary factory buildings. Can an ordinary factory building become a clean workshop by installing FFU?。

Pollution load and operating conditions affect site results

For the same FFU system, the on-site grades obtained under different pollution loads may be different. The number of personnel, unpacking of materials, dust generation from the organization, exhaust switching and door opening frequency will all change the particle concentration.

Verification should be conducted in designated areas and states. Static passing does not mean dynamic passing, and empty state passing does not mean passing production status. If only the bottom of the air supply outlet is measured, it may mainly reflect the fresh filtered air flow, leaving out local pollution caused by personnel, equipment and boundaries. The sampling point layout can be referred to Why can’t the sampling point be located just below the air supply outlet?。

If there is dust at the workstation but the FFU is operating normally, the source of the pollution and the sealed bypass should be checked first instead of directly identifying the FFU as failed. For related troubleshooting methods, please refer to The FFU is running normally, why is dust falling at the workstation?。

Division of labor between device-side EFU and room FFU

The room FFU mainly participates in the background environment air supply, and the equipment-side EFU mainly protects the internal or local operating areas of the designated equipment. The two can cooperate, but the protection boundaries, wind sources and control linkage must be clearly defined respectively.

The logic of this division of labor lies in The division of labor between device-side EFU and room FFU is explained in detail. Device side EFU can be referred to EFU equipment end fan filter unit , room background air supply can be referred to FFU clean air supply products。

If multiple areas require partition duty and troubleshooting, they can be combined FFU group control system provides unified management.

Filter selection and system resistance

Filter selection should correspond to the target particle size and cleanliness level.The HEPA and ULPA filter pages have parameters for different levels of products. When selecting, check the efficiency of the specific model at the target air volume.

Higher filtration efficiency does not necessarily improve site grade. If the particles mainly come from downstream dust production, seal leakage or airflow backflow, upgrading the filter cannot solve the root cause; if the increase in resistance leads to a decrease in air volume, it may also weaken effective protection. Related analysis can refer to Does higher filtration efficiency necessarily lead to improved site ratings?。

Excessively high wind speeds facing the filter may also increase resistance, power consumption and noise. For specific impacts, please refer to What will be the impact if the wind speed facing the filter is too high?。

Project judgment example

A batch of high-efficiency FFU was purchased for a project. The factory test data were normal, but the particles in the room were still high after installation. The investigation found that the return air outlet was blocked by shelves, the air flow was short-circuited in some areas, people came in and out of the door frequently and the enclosure was not sealed. Adjustment methods: Clean the return air channel, increase inlet isolation, and rebalance the air volume in each area. After the adjustment, the on-site particles dropped significantly, and the FFU was not replaced.

Another project uses EFU in the equipment cavity. The static wind speed is normal, but particles appear on the product after the robot moves. The investigation found that the manipulator blocked part of the air supply surface. Adjustment method: Offset the EFU position and increase door opening linkage instead of increasing the number of FFU in the entire room.

These two situations illustrate that FFU is part of the system and cannot independently determine the clean room grade. On-site results need to be comprehensively judged based on system conditions, pollution load and operating status.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

Aili Industry covers motor manufacturing, independent research and development and production of fans, control system development, sheet metal processing, air filter manufacturing and complete machine assembly. For FFU and clean level projects, FFU, EFU, HEPA/ULPA filters, group control systems, air volume, static pressure, and installation interfaces can be uniformly checked to connect equipment configuration with on-site evaluation boundaries and reduce the disconnect between component parameters and complete machine operating conditions.

learn FFU clean air supply products；EFU equipment side fan filter unit；HEPA and ULPA filters；FFU group control system checks the installation space, operating conditions and filtered air supply configuration.

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