Cleanroom Design Explained: ISO 14644-1 and Implementation

  1. What Is a Cleanroom Used for?
  2. Cleanroom Standards: ISO 14644-1 and Other Standards
  3. Key Considerations in Cleanroom Design
  4. Conclusion

Cleanrooms are essential in industries where even the smallest particle can cause serious problems. From semiconductor manufacturing to pharmaceutical production, clean environments help ensure product quality and safety. To build and maintain an effective cleanroom, it’s important to follow proper design and strict standards, such as ISO 14644-1. This article explains what cleanrooms are used for, breaks down the basics of cleanroom design, and outlines the key points of ISO 14644-1 and how to implement them.

 

What Is a Cleanroom Used for?

 

 

A cleanroom is a controlled environment designed to manage airborne particles, temperature, humidity, airflow patterns, and potential sources of contamination. Cleanrooms are widely used across various industries, including semiconductor manufacturing, pharmaceuticals, optics, aerospace, and medical device production.

However, it's important to note that each industry and product requires different processing environments. Cleanrooms must be designed according to specific requirements of the intended application. The primary international standard for cleanroom design is ISO 14644-1, along with several related or legacy standards that continue to be referenced in specific industries. These standards will be discussed in detail in the following section.

 

Cleanroom Standards: ISO 14644-1 and Other Standards

 

Before beginning cleanroom design, it's essential to determine the appropriate cleanroom classification level based on industry requirements and product specifications. Selecting an unsuitable cleanroom grade can directly impact product yield, production efficiency, and overall business competitiveness. Therefore, cleanroom design must comply with relevant industry regulations and technical requirements to ensure optimal performance and reliability.

  • ISO 14644-1 (International Standard)

    ISO 14644-1 is the current global mainstream standard for cleanrooms. It classifies cleanrooms from ISO Class 1 to ISO Class 9 based on the number of particles with a size ≥0.1μm per cubic meter of air. In general, the smaller the ISO number, the cleaner the environment—ISO Class 1 is the cleanest, and ISO Class 9 is similar to regular room air.

    ClassMaximum particles/m³aFED STD 209E Equivalent
    ≥0.1 µm≥0.2 µm≥0.3 µm≥0.5 µm≥1 µm≥5 µm
    ISO 110bdddde-
    ISO 210024b10bdde-
    ISO 31,00023710235bdeClass 1
    ISO 410,0002,3701,02035283beClass 10
    ISO 5100,00023,70010,2003,520832d, e, fClass 100
    ISO 61,000,000237,000102,00035,2008,320293Class 1,000
    ISO 7ccc352,00083,2002,930Class 10,000
    ISO 8ccc3,520,000832,00029,300Class 100,000
    ISO 9ccc35,200,0008,320,000293,000Room air

    Notes:

    1. All concentration values are cumulative.
    2. May require large air sample volumes or sequential sampling.
    3. Not applicable due to extremely high particle levels.
    4. Too few particles to measure accurately.
    5. Sampling errors may occur due to low concentration or particle losses.
    6. For ISO Class 5, particles $\ge 5.0 \ \mu\text{m}$ have special requirements.

 

  • FED STD 209E (U.S. Standard)

    FED STD 209E was an early U.S. cleanroom standard that classified cleanrooms based on the number of airborne particles ≥0.5 μm per cubic foot of air (ranging from Class 1 to Class 100,000). The classification ranges from Class 1 (cleanest) to Class 100,000 (least clean). Although this standard was officially replaced by ISO 14644-1 in 2001, it is still used in certain industries, such as defense and aerospace. The main equivalence between the two standards is as follows:


    FED STD 209EISO 14644-1
    Class 1ISO 3
    Class 10ISO 4
    Class 100ISO 5
    Class 1,000ISO 6
    Class 10,000ISO 7
    Class 100,000ISO 8

  • GMP (Pharmaceutical Cleanroom Standards)

    GMP cleanroom standards are used in pharmaceutical manufacturing to ensure product safety and sterility. The table below shows the maximum allowable levels of airborne particles in cleanrooms, both in the "at rest" (equipment installed, no people present) and "in operation" (normal working conditions) states.


    Maximum Permitted Airborne Particulate Concentration During Classification


    GradeMaximum limits for particulates
    ≥0.5 µm/m³    		Maximum limits for particulates
    ≥5 µm/m³
    at restin operationat restin operation
    A3,5203,520not applicablenot applicable
    B3,520352,000not applicable2,900
    C352,0003,520,0002,90029,000
    D3,520,000not applicable29,000not defined

     

    The second table lists the microbial limits for cleanroom qualification, which help ensure microbiological control in critical environments:


    Limits for Microbial Contamination During Qualification


    GradeAir sample
    cfu/m³    		Settle plates (90 mm)
    cfu/4 hours    		Contact plates (55 mm)
    cfu/plate
    ANo growth
    B1055
    C1005025
    D20010050

 

Key Considerations in Cleanroom Design

 

  • Cleanroom Airflow Pattern Selection

    - Laminar Flow:

    Suitable for high cleanliness requirements (ISO Class 2-5). Air flows in a single direction, either vertically or horizontally, allowing contaminants to be quickly removed.

    - Turbulent Flow:

    Suitable for lower cleanliness requirements (ISO Class 6-8). Contamination is controlled through high-efficiency filtration systems and air circulation.

    - Mixed Flow:

    A combination of laminar and turbulent flow designs. This approach enhances the effectiveness of specific clean zones within the cleanroom.


    To illustrate how different airflow patterns are applied in practice, the following example focuses on microelectronics cleanrooms, where cleanliness requirements vary across work zones.

    Processes like photolithography and wafer fabrication are highly sensitive to particles and typically require unidirectional (laminar) airflow to remove contaminants quickly.

    In contrast, support zones and utility areas, which do not involve direct contact with sensitive components, can tolerate higher particle levels and typically use non-unidirectional (turbulent or mixed) airflow.


    The table below shows how different airflow patterns correspond to various ISO cleanroom classifications and typical applications.

    Air cleanliness class
    (ISO Class) in operation    		Airflow typeAverage airflow velocity
    (m/s)    		Air changes per hour
    (m³/m²·h)    		Examples of applications
    2Unidirectional (Laminar Flow)0.3 to 0.5naPhotolithography, semiconductor processing zone
    3Unidirectional (Laminar Flow)0.3 to 0.5naWork zones, semiconductor processing zone
    4Unidirectional (Laminar Flow)0.3 to 0.5naWork zones, multilayer masks processing, fabrication of compact discs, semiconductor service zone, utility zones
    5Unidirectional (Laminar Flow)0.2 to 0.5naWork zones, multilayer masks processing, fabrication of compact discs, semiconductor service zone, utility zones
    6Non-unidirectional or Mixed (Turbulent or Mixed Flow)na70 to 160Utility zones, multilayer processing, semiconductor service zones
    7Non-unidirectional or Mixed (Turbulent or Mixed Flow)na30 to 70Service zones, surface treatment
    8Non-unidirectional or Mixed (Turbulent or Mixed Flow)na10 to 20Service zones
    NOTE:
    na = not applicable

  • Filtration System




    - High-Efficiency Particulate Air (HEPA) Filters:

    Remove 99.97% of particles ≥0.3μm in size. Commonly used in ISO Class 5-9 cleanrooms.

    - Ultra-Low Penetration Air (ULPA) Filters:

    Provide filtration efficiency up to 99.9995% for particles ≥0.12 μm. Typically used in environments requiring ISO Class 1 to 4.

    - Fan Filter Unit (FFU):

    Suitable for modular cleanrooms, providing stable airflow and enhancing cleanliness.

 

  • Environmental Control

    - Temperature Control:

    Typically maintained between 20-24°C. Some precision manufacturing processes (such as semiconductor production) may require more precise temperature ranges.

    - Humidity Control:

    The common range is 30-60% RH to prevent static electricity (low humidity) or microbial growth (high humidity).

    - Pressure Control:

    • Positive Pressure: Prevents external contaminants from entering the cleanroom. Suitable for electronics, pharmaceutical, and precision manufacturing industries.
    • Negative Pressure: Ensures internal contaminants do not escape. Appropriate for biosafety laboratories and medical isolation wards.

 

Conclusion

 

Cleanroom design requires careful planning, compliance with international standards like ISO 14644-1, and attention to key factors such as airflow, filtration, and environmental control. Different industries and applications demand varying levels of cleanliness, making customized cleanroom design essential for ensuring product quality and operational efficiency.

With years of experience, ACDT provides expert cleanroom design, installation, and maintenance services. Backed by a team of experienced engineers, ACDT helps businesses maintain optimal cleanroom performance with reliable after-sales service.

For customized cleanroom solutions or consultation, feel free to contact ACDT for assistance.

 

 2025-12-01