FFU (Fan Filter Unit) is a key component in cleanroom systems, designed to filter and deliver clean air in a unidirectional flow. While FFUs are typically installed without ductwork, many engineers and facility managers wonder:
Can an FFU be connected to an air duct?

The short answer is: YES, but it depends on specific technical conditions. Let’s explore this topic in detail.

1. Standard Design of FFU (Fan Filter Unit)

Most FFU (Fan Filter Unit) models are designed with open-top or side inlet configurations, allowing them to draw air directly from the cleanroom environment. The internal fan then forces the air through a HEPA or ULPA filter and discharges it vertically in a laminar flow.

  • No ductwork required by default: Standard FFUs are meant to recirculate clean air from the room itself without any external air duct connection.

  • Stable pressure balance: A properly designed return and supply airflow system maintains positive pressure inside the cleanroom.

2. Is It Possible to Connect an Air Duct to an FFU (Fan Filter Unit)?

✅ Technically, yes — but only under certain conditions:

Adequate static pressure is required

  • Standard FFU fans have static pressures around 50–150 Pa, which is insufficient for handling long or complex ductwork.

  • If ducting is necessary, you must use a high static pressure FFU (≥200 Pa) or integrate a booster fan into the system.

Optimized duct design is essential

  • Ducts should be as short, straight, and smooth as possible.

  • Avoid sharp turns, narrow sections, and long runs that increase resistance.

  • The duct size must match the FFU inlet to prevent turbulence and maintain airflow integrity.

Uniform airflow must be ensured

  • Improper duct design can cause uneven air distribution or localized negative pressure, reducing filtration efficiency.

3. When Should You Connect an Air Duct to an FFU (Fan Filter Unit)?

Connecting an air duct to an FFU (Fan Filter Unit) should only be considered when all technical requirements are met:

✅ Recommended scenarios (with proper conditions):

  1. Air supply from an HVAC system

    • Ideal for environments requiring temperature and humidity control.

  2. Prevent contamination at air intake

    • Useful when drawing air from higher-grade clean zones or isolated sources.

  3. Short-distance local supply

    • For example: delivering air to an enclosed workspace or equipment area (≤2 meters duct length).

  4. Customized cleanroom systems

    • With pressure calculations, duct resistance analysis, and airflow simulation (e.g., CFD modeling).

❌ Not recommended in the following cases:

  • Long or branched duct systems.

  • Use of standard FFUs with low static pressure.

  • Critical cleanroom applications (e.g., ISO Class 3 or higher), where airflow fluctuations are unacceptable.

  • Lack of proper system balancing and post-installation testing.

4. Key Considerations When Connecting FFU (Fan Filter Unit) to Ductwork

To ensure optimal performance, follow these best practices:

  • Verify duct design using simulation or actual measurement

    • Confirm total pressure loss does not exceed FFU capability.

  • Post-installation system testing

    • Measure actual airflow velocity and volume.

    • Check cleanroom differential pressure.

    • Perform HEPA integrity testing (DOP/PAO method if applicable).

  • Routine maintenance

    • Clean the duct regularly to avoid dust buildup.

    • Monitor fan performance and adjust speed using VFD (if available).

5. Conclusion: Is Duct Connection Feasible for FFU (Fan Filter Unit)?

Yes, duct connection is feasible — but only with high static pressure FFUs, optimized duct design, and careful system planning.

Recommended:

  • Use standard FFU (Fan Filter Unit) configurations without ducting when possible to maximize reliability and minimize complexity.

Optional:

  • If duct connection is necessary, consult with both the FFU manufacturer and your cleanroom designer to ensure system compatibility and performance.

✅ Need Cleanroom FFU Consultation?

Vietnam Cleanroom (VCR) specializes in cleanroom equipment and custom filtration solutions. Whether you're designing a duct-connected FFU system or looking for high static pressure models, we're here to help.

Hotline: +84 90 123 9008 (Zalo/Phone 24/7)
Email: [email protected]
Website: https://vietnamcleanroom.com