Fan Filter Units

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When we work in a biotech lab, semiconductor lab, or hospital intensive care unit (ICU), we need to use fan filter units to control contamination and keep the air clean in a sterile environment. Fan filter units are essential equipment in clean rooms.

What is a fan filter unit?

A fan filter unit has two main components, a high-efficiency air filter (usually HEPA or ULPA) and an integrated fan or blower. The main function of the FFU is to draw in contaminated air from above and push clean filtered air downward into the workspace to ensure optimal air quality.

How a Fan Filter Unit Works？

Fan filter units (FFUs) work by actively filtering contaminants from the air, creating a clean, controlled environment. The FFU principle of operation can be simply divided into five steps:

1. The FFU draws air from the surrounding environment, usually from the static pressure box space above the ceiling grid or the circulating air in the clean room. This air may contain dust, pollen, microorganisms, or other airborne particles that are not allowed to enter sensitive work areas.
2. Before the incoming air reaches the main filter, it usually passes through a pre-filter. This initial filter captures larger particles such as hair, dust and lint. It helps to extend the life of the more expensive main filter and keep the internal components of the equipment clean.
3. The air then flows through a HEPA (High Efficiency Particulate Air) or ULPA (Ultra-Low Penetration Air) filter:
   HEPA filters remove at least 99.97% of particles ≥ 0.3 microns.
   ULPA filters remove 99.9995% of particles ≥ 0.12 microns.
   During this stage, tiny particles such as bacteria, viruses, fine dust and even smoke particles are captured, making the air ultra-clean.
4. Inside the unit, a centrifugal or backward-inclined fan (driven by an ECM or PSC motor) provides airflow. The fan ensures that sufficient air pressure is maintained to push the filtered air downward and evenly distribute it throughout the cleanroom space. This step is what differentiates the FFU from a passive filter – it does more than just clean the air; it actively moves the airflow, controlling airflow speed and volume.
5. Finally, the filtered air is exhausted in a uniform laminar (one-way) flow through a diffuser or grille. This helps reduce turbulence and prevents particles from being stirred within the workspace. This clean, uniform airflow protects sensitive processes, products or patients from airborne contamination.

Types of fan filter units

Based on the filter type, they can be divided into HEPA fan filter units, ULPA fan filters

1.HEPA Fan Filter Units

These units are equipped with high-efficiency particulate air (HEPA) filters. They are designed to capture 99.97% of particles ≥ 0.3 microns, including dust, pollen, bacteria and mold spores. They can be used in electronic, automotive cleanrooms, and most general cleanroom applications. The main advantages are that they are economical, energy-efficient, and highly reliable.

2.ULPA Fan Filter Units

Ultra-low penetration air (ULPA) filters go a step further and capture 99.9995% of particles ≥ 0.12 microns. They are mainly used in pharmaceutical laboratories, nanotechnology, biotechnology, and other supercritical environments.The benefit is excellent particle removal, but they are usually more expensive and have more restrictions on airflow.

What are modular fan filter units?

Modular Fan Filter Units are pre-assembled, self-contained filtration units that can be added or removed from a cleanroom system individually. Each unit contains a fan, a HEPA or ULPA filter, and typically includes a built-in speed or power controller. These units are designed to mount to a standard ceiling grid, wall, or portable cabinet. Unlike traditional HVAC systems or built-in cleanroom air filtration units, modular FFUs offer plug-and-play simplicity, scalability, and cost-effectiveness without sacrificing performance.

These units easily install into a standard 2ft x 2ft or 2ft x 4ft ceiling grid. Modular Fan Filter Units eliminate the need for expensive and complex central HVAC upgrades. You only pay for the air filtration you need. Each unit can be maintained individually without affecting the rest of the system. When it’s time to replace a filter, only one unit needs to be replaced without shutting down the entire cleanroom. Because FFUs operate independently, if one unit fails, the others can continue to operate. This reduces the risk of total system failure and maintains the integrity of the cleanroom.

How to Install a Fan Filter Unit

Installing a fan filter unit (FFU) may sound like an engineer’s job, but thanks to modern designs, it’s surprisingly easy. Whether you’re installing in a cleanroom ceiling grid, laminar flow cabinet, or modular clean area, following the right procedures will ensure safe operation, optimal airflow, and lasting filtration performance. Watch our installation video!

The Role of FFUs in ISO Certification

FFUs not only support high-efficiency air filtration but also help facilities meet the strict requirements outlined in ISO 14644-1, the international standard for cleanroom classification.

Understanding ISO Cleanroom Classifications

ISO 14644-1 sets cleanliness standards for controlled environments, measuring airborne particle concentrations per cubic meter. Classifications range from ISO Class 1 (most stringent) to ISO Class 9 (least stringent).

How FFUs Help Achieve ISO Certification

1. Particle Control Through Filtration

FFUs use HEPA or ULPA filters, capable of capturing up to 99.9995% of particles as small as 0.12 microns. This level of filtration is necessary to reduce airborne particles and meet ISO particle count limits, especially in ISO Classes 5 through 7.HEPA filters are sufficient for ISO Class 7–8 cleanrooms.ULPA filters are typically used for ISO Class 5–6 environments.

2. Laminar Airflow for Clean Zones

FFUs produce laminar (unidirectional) airflow, which sweeps contaminants away from cleanroom surfaces and prevents them from resettling. This kind of airflow pattern is a requirement for maintaining ISO-certified conditions, especially in critical process areas.

FFUs Integration with HVAC Systems

Integrating Fan Filter Units (FFUs) with existing or new HVAC systems offers a hybrid approach to air handling that enhances cleanroom performance, energy efficiency, and operational control. While FFUs are often thought of as standalone units in modular or localized clean zones, they can also work in tandem with centralized HVAC systems to create robust, adaptable cleanroom environments.

Why Integrate FFUs with HVAC Systems?

Standalone FFUs are great for modular cleanrooms and point-of-use filtration, but they can do much more when strategically combined with HVAC infrastructure. Here’s why integration makes sense:

• To pre-condition air (temperature and humidity) before it enters the FFUs
• To maintain building-wide pressure balance between clean and non-clean areas
• To improve airflow control and zoning flexibility
• To reduce the burden on HVAC systems by offloading air filtration to FFUs
• To achieve tight control of ISO class environments, especially in larger facilities

Fan Filter Unit and Particle Counters

When paired with a Fan Filter Unit (FFU), particle counters provide real-time data to verify cleanliness levels, monitor performance, and ensure compliance with standards like ISO 14644-1, GMP, and USP 797/800.

What Is a Particle Counter?

A particle counter is an instrument that detects and counts airborne particles in a specific volume of air. It helps verify whether an environment meets the required cleanliness levels by:

• Measuring particle sizes (commonly ≥0.3 µm and ≥0.5 µm)
• Counting particles per cubic meter or foot of air
• Logging data over time for trend analysis and audits

These counters are essential for ISO certification, environmental monitoring, and contamination control in industries like pharmaceuticals, electronics, aerospace, and healthcare.

How Particle Counters and FFUs Work Together

FFUs actively clean the air by drawing it through a HEPA or ULPA filter and discharging it in a laminar flow. Particle counters sample the air in real time—either directly from a cleanroom or near the FFU’s airflow output.The data is compared to target thresholds set by ISO Class or GMP levels.If particle levels exceed acceptable limits, an alarm is triggered, or FFU performance can be adjusted automatically.

Applications of FFUs in Modular Cleanrooms