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Understanding Laminar Flow in a Cleanroom

June 9, 2023
Understanding Laminar Flow in a Cleanroom

Laminar Flow in Cleanrooms

Laminar flow plays a crucial role in maintaining the pristine environment within a cleanroom. Intentionally placed filters create unidirectional flow of air by controlling the speed and direction of clean, filtered air, and force contaminating particles into plenums for either outside disposal or re-circulation back through a filter. Here we will dive into the fundamentals of laminar flow and explain how it can be used to optimize your cleanroom.

What is Laminar Flow?

Laminar flow refers to a type of fluid flow in which the fluid moves smoothly and uniformly in parallel layers, with little to no disruption between them. This type of flow is characterized by a consistent velocity and direction, typically moving in a single direction from a clean area to a less clean area.

There are two primary types of laminar airflow systems:

  1. Unidirectional Laminar Flow: In this system, air moves in a single direction, typically from a filter located at the top of the clean area downward towards the working area or personnel. This setup creates a controlled and clean environment by constantly displacing airborne particles away from critical processes or areas.
  2. Horizontal Laminar Flow: Here, air flows horizontally from a filter located at one end of the clean area towards an extraction point on the opposite end.

Laminar airflow is achieved through the use of high-efficiency particulate air (HEPA) filters or ultra-low particulate air (ULPA) filters. These filters remove a significant percentage of particles from the air, ensuring that the air entering the controlled environment is clean and free from contaminants.

How is Laminar Flow Used in a Cleanroom?

In the context of a cleanroom, laminar flow is defined as airflow that is uniform in both direction and velocity. This helps maintain cleanliness by controlling the speed and direction of clean, filtered air and allowing for effective creation pressure gradients. Laminar flow prevents cross-contamination and makes particle distribution both predictable and controlled. When used in a cleanroom, laminar flow allows for contaminants to be moved away from operating surfaces and back through filters at a controlled air exchange rate.

To create laminar airflow in a cleanroom, several factors and design considerations need to be taken into account.

  1. Airflow Direction: Air is pushed through HEPA or ULPA filters in a single direction, either downward or horizontally.
  2. Air Supply Plenum: A space or chamber located above the cleanroom's ceiling. This plenum distributes the filtered air evenly across the entire ceiling surface of the cleanroom.
  3. Return Air: Provide adequate return air paths or exhaust grilles at the lower level of the cleanroom. These paths allow the air to be recirculated or extracted, maintaining the proper balance of airflow and preventing the buildup of contaminants.
  4. Airflow Velocity: Ensure that the velocity of the airflow is within the specified range for laminar flow. Typically, laminar flow velocities range from 0.3 to 0.5 meters per second (60 to 100 feet per minute), but this can vary depending on the specific cleanroom class and requirements.
  5. Proper Sealing: Seal all openings, joints, and penetrations in the cleanroom's walls, ceiling, and floor to prevent unfiltered air from entering and disrupting the laminar flow. Pay attention to doors, windows, electrical outlets, and any other potential sources of air leakage.
  6. Regular Maintenance: Regularly inspect and maintain the cleanroom's filtration system, including the HEPA or ULPA filters, to ensure their proper functioning. Replace filters as recommended by the manufacturer to maintain efficient particle removal.

Laminar Flow vs. Turbulent Flow

Where laminar airlfow moves in parallel, unmixed layers, turbulent airflow is characterized by irregular and chaotic movement. This pattern promotes particle dispersion throughout the space and is incredibly difficult to control or predict. Particle distribution is uneven and can create areas of high contamination. Whenever possible, design sterile environments to utilize laminar airflow to ensure controlled, particle free air that can pass regular inspection.


Laminar flow is crucial for maintaining the pristine conditions of a cleanroom by minimizing disruption and ensuring uniform airflow. It effectively displaces airborne particles, preventing cross-contamination and allowing for controlled particle distribution. By implementing proper design considerations and maintenance, cleanrooms can optimize their operations and uphold the highest standards of cleanliness and contamination control through the utilization of laminar flow. If you are unsure how to design your cleanroom in a way that optimizes laminar airflow, don’t hesitate to reach out to the experts at Instant Cleanroom and we will work to design a custom solution for your operation.