What is FFU? Considerations When Using FFU

FFU, which stands for Fan Filter Unit, is an air filtration device widely used in cleanrooms to provide clean and uniform airflow, ensuring a safe and standardized working environment. So, what exactly is FFU? How is it structured, how does it work, and what should be considered when using FFU? Let’s explore with INTECH Service in the article below.

What is FFU?

FFU, or Fan Filter Unit, is a box-shaped air filtration device used in cleanrooms to provide clean and controlled airflow by removing harmful particles from the circulating air.

It is one of the most common devices in cleanrooms. It can be used to supply clean air to a large cleanroom or provide localized clean air for other equipment. FFUs are typically installed in ceiling grid systems. For large cleanrooms, the number of required units can range from a few hundred to several thousand.

FFUs play a crucial role in ensuring a safe and high-quality production environment for industries such as pharmaceuticals, healthcare, electronics, and food processing.

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Structure of FFU

The structure of FFU may vary depending on the manufacturer and model. However, typically, an FFU consists of the following five components: Casing, Fan, Filter, Perforated Face, Control Unit.


Made of electrostatically painted steel or stainless steel.

Protects the internal components of the FFU from dust and external impacts.

May be designed for easy disassembly for cleaning purposes.


Provides airflow through the filter.
The type of fan commonly used is either a centrifugal fan or an axial fan.

The fan is selected based on the required air volume and pressure for the cleanroom.


Removes dust particles, microorganisms, and other contaminants from the air.

The types of filters commonly used are pre-filters and fine filters (HEPA or ULPA). Pre-filters function to remove coarse dust, providing good protection for the downstream fine filter and also help to clean a portion of the dust before the air passes through the HEPA filter layer. HEPA filters capture ultrafine particles, with a size of 0.3 microns, with a filtration efficiency of 99.97%.

The filtration efficiency of the filter is evaluated by efficiency grade (E) or filtration class (U).

Perforated Face:

Distributes airflow evenly and uniformly in the cleanroom.

Made of stainless steel or aluminum.

May be designed with holes or slots to adjust airflow direction and volume.

The perforated face serves to evenly diffuse the airflow vertically downward into the cleanroom area.

Control Unit:

Controls on/off and fan speed for the cleanroom FFU as per usage requirements.

In addition, FFUs may be equipped with additional components such as:

Sensors: Monitor environmental parameters in the cleanroom such as temperature, humidity, pressure, etc.

Indicator lights: Indicate the operational status of the FFU.

cau tao ffu

Operating Principle of FFU

In general, FFUs operate based on the principle of drawing in dirty air from the outside, filtering it through HEPA/ULPA filters, and then delivering clean air into the cleanroom.

Suction process:

FFUs use a fan (comprising a motor and fan blades) to draw air from the outside.

Depending on specific requirements, FFUs may be equipped with a pre-filter before the fan. The pre-filter helps remove large dust particles, facilitating faster filtration and ensuring the efficient and long-term operation of HEPA/ULPA filters.

Delivery process:

After being drawn in, the air passes through HEPA or ULPA filters.

The filtered air is then delivered into the cleanroom through a perforated face at a velocity of 0.45m/s ± 20%. Clean air is supplied downward vertically into the designated cleanroom area.

nguyen ly hoat dong ffu

Classification of FFU

FFUs (Fan Filter Units) can be classified based on various criteria, including:

Classification of FFU by Frame Size

Standard Size FFU: 1175x575x250 (including filter)

Small Size FFU: 575x575x250 (including filter)

Classification of FFU by Frame Material

Electrostatically Painted FFU: Provides high aesthetics, dust repellence, and ensures cleanroom standards.

Stainless Steel 304 FFU: Resistant to corrosion, suitable for chemical environments, high aesthetics.

Galvanized Steel FFU: Cost-effective.

Classification of FFU by Motor Type

EC Motor FFU: Energy-efficient, smooth operation.

AC Motor FFU: Economical, suitable for basic requirements.

Classification of FFU by Filter Type

HEPA FFU: Filters 99.97% of dust particles sized 0.3 microns.

ULPA FFU: Filters 99.999% of dust particles sized 0.1 microns.

Considerations When Using FFU

Ensure the operational environment of the FFU meets standards: Humidity: below 85% RH (no condensation), cleanliness level: Class 100 – 10,000. If not operating under these conditions, the performance and lifespan of the FFU may be affected.

Proper installation location of FFU: Avoid placing FFUs near heaters, kitchens, or other electrical sources, and do not place combustible materials or chemicals near FFUs to prevent the risk of fire or explosion. Do not use sulfuric acid, hydrochloric acid, bleach, and other chemicals near the filter unit as they may cause corrosion and damage to the equipment.

Proper installation of FFU air filters: Do not exert excessive force directly on the FFU air filter body to avoid deformation. Absolutely do not operate the machine with wet hands to prevent electric shock. Do not block the intake and outlet ports of the machine. If the intake and outlet ports of the machine are blocked, the operation of the machine will not be normal, leading to abnormal machine functions or damage to electrical components.

lap dat ffu

Maintenance, regular inspection: Maintenance and inspection help ensure the efficient and long-term operation of the FFU, so you should perform this regularly. However, do not attempt to inspect or disassemble or repair without experience; instead, use maintenance services from reputable and professional units.

How often should FFU maintenance be performed?

After operating for 3 months, FFUs need regular inspection of the fan guard. If there is loosening of the screws, tighten them to ensure safety during use.

If the fan speed control unit malfunctions, such as the speed increasing or the air volume of the FFU not changing significantly, it needs immediate repair by replacing the capacitor or SCR.

If testing reveals that HEPA filters are damaged, the air velocity decreases significantly, or the performance is not achieved, notify the manufacturer or supplier immediately for replacement or repair of the HEPA filter.

In addition, for FFUs using HEPA filters, it is recommended to replace the HEPA filter once a year, or earlier if necessary. For FFUs using ULPA filters, it is recommended to replace the ULPA filter every two years, or earlier if necessary.

The above are information about the concept, structure, and considerations when using FFU. Hopefully, the information above has helped you understand more about FFU Fan Filter Units. If you still have any questions or need further advice, please contact INTECH Service for detailed consultation.