In cleanroom environments, the typical velocity range for laminar flow is 0.36 to 0.45 meters per second (m/s). This range is considered optimal for controlling particle contamination without causing turbulence. The widely accepted industry standard is 0.45 m/s as it provides a good balance between removing particles and maintaining stable airflow.

• 0.36 m/s is often used in less critical cleanroom environments or areas where minimizing energy consumption is a priority.
• 0.45 m/s is the standard for more stringent cleanroom applications like semiconductor manufacturing, pharmaceutical production, and other sensitive operations where particle control is critical.

Why 0.45 m/s?

• Particle Transport and Removal: At 0.45 m/s, the air velocity is high enough to continuously displace airborne particles and prevent them from settling onto surfaces. This is critical for maintaining the cleanliness class of the room, especially in ISO Class 5 or 6 cleanrooms.
• Minimizing Turbulence: Higher velocities can cause turbulence, which disrupts the laminar flow and stirs up contaminants. A velocity of 0.45 m/s provides a controlled, unidirectional flow that minimizes the chance of turbulence and ensures contaminants are efficiently swept out of the cleanroom.
• Compliance with ISO and GMP Standards: Cleanrooms operating under ISO Class 5 (or better) and GMP guidelines require the air velocity to remain in the range of 0.36–0.45 m/s to ensure consistent performance and compliance with regulatory standards.

Cleanroom Applications and Examples

1. Semiconductor Manufacturing
   • FFUs with 0.45 m/s airflow ensure particles are continuously removed, protecting the wafers from contamination.
   • Turbulence is minimized, preventing particle deposition on critical components.
   • This air velocity is essential to maintain laminar flow throughout the cleanroom, ensuring that particles move in a controlled manner away from sensitive zones.
2. Pharmaceutical Cleanrooms
   • Laminar flow hoods and FFUs providing air at 0.45 m/s create a protective envelope of sterile air around work areas.
   • The air velocity helps prevent contamination from personnel and equipment, ensuring a higher level of product safety and reducing the risk of contamination from airborne particles.
3. Biotechnology and Medical Device Manufacturing
   • Laminar flow ensures controlled particle movement, reducing contamination risk on medical devices that must remain sterile.
   • The air velocity of 0.45 m/s ensures a stable, controlled airflow, essential for both product quality and regulatory compliance.

Air Changes per Hour (ACH)

The laminar flow velocity also affects the number of air changes per hour in the cleanroom. For example:

• In an ISO Class 5 cleanroom, the standard ACH is around 240 to 600 air changes per hour. To meet this, FFUs with 0.45 m/s air velocity ensure enough clean air supply to replace contaminated air and remove particles from the room.
• Laminar flow units operating at this velocity contribute significantly to achieving these air changes by providing a constant flow of filtered air from HEPA filters.

Energy Considerations

While 0.45 m/s is the industry standard for cleanroom applications requiring high cleanliness levels, lower velocities (e.g., 0.36 m/s) are sometimes considered to reduce energy costs:

• Reducing the velocity lowers the fan energy needed to drive the airflow through HEPA filters.
• However, any reduction in air velocity must be carefully evaluated to ensure that it doesn’t compromise the cleanroom’s ability to meet particle control requirements.

Technical Design Impact

When designing cleanroom systems like FFUs or Laminar Flow Units:

• The selected airflow velocity of 0.45 m/s directly affects the pressure drop across the HEPA or ULPA filters. Higher velocities require more fan power to overcome this resistance.
• Pressure monitoring devices (e.g., Magnehelic gauges) are often installed to ensure that the filters are operating within the required parameters at this velocity.
• Proper placement of FFUs and laminar flow units ensures that the air moves uniformly across the cleanroom without creating dead zones where particles can accumulate.
• Maintaining pressure differentials between cleanrooms and adjacent spaces is another critical factor supported by maintaining the proper laminar flow velocity.