The selection of the fan filter unit (FFU) directly affects the purification effect, operating cost and stability of the cleanroom, and needs to be comprehensively evaluated in combination with specific application scenarios. The following are the core factors that need to be given priority consideration when making a selection:
I. Cleanliness Requirements
This is the primary basis for selection, determining the type and performance parameters of the filter:
Particle size and filtration efficiency
If a Class 1000 to 100,000 cleanroom is required (such as for general electronic assembly and food processing), a HEPA filter (with an efficiency of ≥99.97% for 0.3μm particles) is sufficient.
If Class 1 to 100 is required (such as in semiconductor wafer manufacturing, biomedicine aseptic workshops), ULPA filters (with an efficiency of ≥99.999% for 0.12μm particles) should be selected.
Air cleanliness grade standards: It is necessary to refer to standards such as ISO 14644-1 and FS 209E, clearly define the maximum allowable particle concentration in the target area, and then invert the filtration efficiency requirements of the FFU.
Ii. Air Volume and air change Rate
Air volume is the core performance parameter of FFU and needs to match the volume and air change rate requirements of the cleanroom
Air change rate calculation The minimum air change rate is determined based on the cleanliness level (for example, ≥300 times /h for Class 100 and ≥150 times /h for Class 10,000), and then the total required air volume is calculated through the formula “Air volume = room volume × air change rate”, and the air volume and installation quantity of each FFU are determined accordingly.
Air volume adjustment range: In some scenarios (such as equipment start-up and shutdown, personnel changes), dynamic adjustment of air volume is required. It is preferred to choose FFUs with stepless speed regulation (such as brushless DC fan models) to ensure that the air volume can be adjusted within the range of 30% to 100%, taking into account both energy conservation and stability of cleanliness.
Iii. Fan Types and Energy Consumption
The fan is the main energy-consuming component of the FFU, and its type directly affects the operating cost
Centrifugal fans: They feature high air pressure and stable air volume, making them suitable for large clean rooms or scenarios where high system resistance needs to be overcome (such as long air ducts and multiple filters). However, they have moderate energy consumption and slightly higher noise levels (approximately 55 to 65dB).
Axial flow fans: They have a large air volume but low air pressure, making them suitable for simple clean rooms with low resistance. They have relatively low energy consumption and low noise (about 50 to 60dB), but their air volume stability is poor and their filtration efficiency is greatly affected by the environment.
Brushless DC fans: They feature high efficiency and energy conservation (30% to 50% more energy-efficient than traditional AC fans), long service life (≥ 50,000 hours), high speed regulation accuracy, and low noise (about 50 to 60dB). They are the preferred choice for high-end clean rooms (such as in the semiconductor and pharmaceutical industries). Although they have a relatively high initial cost, they offer better long-term cost performance.
Iv. Installation Environment and Dimensions
The size and installation method of the FFU need to match the layout of the cleanroom
External dimensions: Common standardized dimensions include 1200×600mm, 1200×1200mm, 600×600mm, etc. They need to match the spacing of the ceiling keel (such as a 600×600mm grid) or the installation frame to avoid installation difficulties or air leakage caused by size mismatch.
Installation method
Ceiling-mounted: Suitable for standardized clean rooms, it is necessary to ensure the load-bearing capacity of the ceiling (the weight of a single FFU is approximately 20 to 40 kilograms).
Bracket type: Suitable for non-standardized areas or temporary renovations, the load-bearing capacity and stability of the brackets need to be considered.
Laminar flow combination: Multiple FFUs are spliced together to form a laminar flow hood. It is necessary to ensure that the splicing points are well sealed to avoid short circuits in the airflow.
Space height limitation: The height of the FFU itself (approximately 300 to 500mm) must match the clear height from the ceiling to the floor to avoid affecting personnel operation or equipment running.
V. Control Mode and Intelligent Requirements
Select the control mode based on the scale of the cleanroom and management requirements:
Single manual control: Suitable for small clean rooms (such as laboratories), with low cost. The wind speed of each FFU can be independently adjusted through a knob, but it is not convenient for centralized management and has relatively high energy consumption.
Centralized control: Multiple FFUs can be uniformly managed through PLC, touch screen or central control system, enabling real-time monitoring of wind speed, wind pressure and fault status. It supports batch start, stop and speed regulation, making it suitable for large clean rooms (such as electronic factories), and facilitating energy conservation and maintenance.
Intelligent interlocking control: By integrating devices such as differential pressure sensors and particle counters, it can achieve automatic adjustment (such as automatically increasing air volume when cleanliness drops), and can be connected to the factory MES system. It is suitable for scenarios with extremely high requirements for cleanliness stability (such as semiconductor lithography areas). The initial investment is high but it can significantly reduce labor costs.
Vi. Noise and Vibration
Cleanroom operators stay indoors for long periods of time and need to control the noise and vibration of the FFU
Noise requirements: For general cleanrooms, the noise level should be ≤65dB (for precision workshops, it should be ≤60dB). When selecting the model, low-noise fans (such as brushless DC fans) should be given priority, and it is necessary to check whether the equipment is equipped with shock-absorbing pads and noise reduction structures to avoid noise amplification due to vibration transmission.
Vibration control: The vibration generated by the fan during operation may affect precision equipment (such as photolithography machines). It is necessary to select a fan with high dynamic balance accuracy or use shock-absorbing brackets to reduce vibration transmission.
Vii. Maintenance and Lifespan
Long-term usage costs and maintenance convenience need to be considered in advance
Filter replacement: The lifespan of HEPA/ULPA filters is typically 1 to 3 years (depending on the environmental dust concentration). When selecting the type, it is necessary to ensure that the filter replacement is convenient (such as side-opening or drawer structure) to avoid complex disassembly that may lead to excessive downtime.
The lifespan of the fan: The lifespan of a brushless DC fan can reach over 50,000 hours, while that of an AC fan is approximately 20,000 to 30,000 hours. The selection should be based on the equipment’s depreciation cycle to reduce the frequency of replacement in the later stage.
Supply of vulnerable parts: Select brands with a large market share to ensure an adequate supply of vulnerable parts such as fans, motors, and filters, thereby reducing maintenance waiting time.
Viii. Cost Budgeting
It is necessary to balance the initial procurement cost and the long-term operating cost
For low-end scenarios (such as temporary clean areas), HEPA + AC centrifugal fan + manual control can be selected. The cost is relatively low but the energy consumption is high.
For high-end scenarios (such as semiconductor workshops), it is recommended to choose ULPA + brushless DC fan + intelligent control. The initial investment is high, but it has good energy-saving performance, long service life, and lower long-term total cost.
In conclusion, the selection of FFU should be based on the cleanliness requirements as the core, and a comprehensive decision should be made by taking into account factors such as air volume, energy consumption, installation environment, and intelligent demands. When necessary, the rationality of the selection can be verified through on-site tests or simulation calculations.
I. Cleanliness Requirements
This is the primary basis for selection, determining the type and performance parameters of the filter:
Particle size and filtration efficiency
If a Class 1000 to 100,000 cleanroom is required (such as for general electronic assembly and food processing), a HEPA filter (with an efficiency of ≥99.97% for 0.3μm particles) is sufficient.
If Class 1 to 100 is required (such as in semiconductor wafer manufacturing, biomedicine aseptic workshops), ULPA filters (with an efficiency of ≥99.999% for 0.12μm particles) should be selected.
Air cleanliness grade standards: It is necessary to refer to standards such as ISO 14644-1 and FS 209E, clearly define the maximum allowable particle concentration in the target area, and then invert the filtration efficiency requirements of the FFU.
Ii. Air Volume and air change Rate
Air volume is the core performance parameter of FFU and needs to match the volume and air change rate requirements of the cleanroom
Air change rate calculation The minimum air change rate is determined based on the cleanliness level (for example, ≥300 times /h for Class 100 and ≥150 times /h for Class 10,000), and then the total required air volume is calculated through the formula “Air volume = room volume × air change rate”, and the air volume and installation quantity of each FFU are determined accordingly.
Air volume adjustment range: In some scenarios (such as equipment start-up and shutdown, personnel changes), dynamic adjustment of air volume is required. It is preferred to choose FFUs with stepless speed regulation (such as brushless DC fan models) to ensure that the air volume can be adjusted within the range of 30% to 100%, taking into account both energy conservation and stability of cleanliness.
Iii. Fan Types and Energy Consumption
The fan is the main energy-consuming component of the FFU, and its type directly affects the operating cost
Centrifugal fans: They feature high air pressure and stable air volume, making them suitable for large clean rooms or scenarios where high system resistance needs to be overcome (such as long air ducts and multiple filters). However, they have moderate energy consumption and slightly higher noise levels (approximately 55 to 65dB).
Axial flow fans: They have a large air volume but low air pressure, making them suitable for simple clean rooms with low resistance. They have relatively low energy consumption and low noise (about 50 to 60dB), but their air volume stability is poor and their filtration efficiency is greatly affected by the environment.
Brushless DC fans: They feature high efficiency and energy conservation (30% to 50% more energy-efficient than traditional AC fans), long service life (≥ 50,000 hours), high speed regulation accuracy, and low noise (about 50 to 60dB). They are the preferred choice for high-end clean rooms (such as in the semiconductor and pharmaceutical industries). Although they have a relatively high initial cost, they offer better long-term cost performance.
Iv. Installation Environment and Dimensions
The size and installation method of the FFU need to match the layout of the cleanroom
External dimensions: Common standardized dimensions include 1200×600mm, 1200×1200mm, 600×600mm, etc. They need to match the spacing of the ceiling keel (such as a 600×600mm grid) or the installation frame to avoid installation difficulties or air leakage caused by size mismatch.
Installation method
Ceiling-mounted: Suitable for standardized clean rooms, it is necessary to ensure the load-bearing capacity of the ceiling (the weight of a single FFU is approximately 20 to 40 kilograms).
Bracket type: Suitable for non-standardized areas or temporary renovations, the load-bearing capacity and stability of the brackets need to be considered.
Laminar flow combination: Multiple FFUs are spliced together to form a laminar flow hood. It is necessary to ensure that the splicing points are well sealed to avoid short circuits in the airflow.
Space height limitation: The height of the FFU itself (approximately 300 to 500mm) must match the clear height from the ceiling to the floor to avoid affecting personnel operation or equipment running.
V. Control Mode and Intelligent Requirements
Select the control mode based on the scale of the cleanroom and management requirements:
Single manual control: Suitable for small clean rooms (such as laboratories), with low cost. The wind speed of each FFU can be independently adjusted through a knob, but it is not convenient for centralized management and has relatively high energy consumption.
Centralized control: Multiple FFUs can be uniformly managed through PLC, touch screen or central control system, enabling real-time monitoring of wind speed, wind pressure and fault status. It supports batch start, stop and speed regulation, making it suitable for large clean rooms (such as electronic factories), and facilitating energy conservation and maintenance.
Intelligent interlocking control: By integrating devices such as differential pressure sensors and particle counters, it can achieve automatic adjustment (such as automatically increasing air volume when cleanliness drops), and can be connected to the factory MES system. It is suitable for scenarios with extremely high requirements for cleanliness stability (such as semiconductor lithography areas). The initial investment is high but it can significantly reduce labor costs.
Vi. Noise and Vibration
Cleanroom operators stay indoors for long periods of time and need to control the noise and vibration of the FFU
Noise requirements: For general cleanrooms, the noise level should be ≤65dB (for precision workshops, it should be ≤60dB). When selecting the model, low-noise fans (such as brushless DC fans) should be given priority, and it is necessary to check whether the equipment is equipped with shock-absorbing pads and noise reduction structures to avoid noise amplification due to vibration transmission.
Vibration control: The vibration generated by the fan during operation may affect precision equipment (such as photolithography machines). It is necessary to select a fan with high dynamic balance accuracy or use shock-absorbing brackets to reduce vibration transmission.
Vii. Maintenance and Lifespan
Long-term usage costs and maintenance convenience need to be considered in advance
Filter replacement: The lifespan of HEPA/ULPA filters is typically 1 to 3 years (depending on the environmental dust concentration). When selecting the type, it is necessary to ensure that the filter replacement is convenient (such as side-opening or drawer structure) to avoid complex disassembly that may lead to excessive downtime.
The lifespan of the fan: The lifespan of a brushless DC fan can reach over 50,000 hours, while that of an AC fan is approximately 20,000 to 30,000 hours. The selection should be based on the equipment’s depreciation cycle to reduce the frequency of replacement in the later stage.
Supply of vulnerable parts: Select brands with a large market share to ensure an adequate supply of vulnerable parts such as fans, motors, and filters, thereby reducing maintenance waiting time.
Viii. Cost Budgeting
It is necessary to balance the initial procurement cost and the long-term operating cost
For low-end scenarios (such as temporary clean areas), HEPA + AC centrifugal fan + manual control can be selected. The cost is relatively low but the energy consumption is high.
For high-end scenarios (such as semiconductor workshops), it is recommended to choose ULPA + brushless DC fan + intelligent control. The initial investment is high, but it has good energy-saving performance, long service life, and lower long-term total cost.
In conclusion, the selection of FFU should be based on the cleanliness requirements as the core, and a comprehensive decision should be made by taking into account factors such as air volume, energy consumption, installation environment, and intelligent demands. When necessary, the rationality of the selection can be verified through on-site tests or simulation calculations.
