What is ISO 14644-1 cleanroom standards?

Cleanrooms are controlled environments with low levels of pollutants that are used in industries where environmental control is critical. The ISO 14644-1 standard sets the specifications and classifications for cleanrooms and associated controlled environments. This international standard aims to establish a consistent basis for designing, building and operating cleanrooms, as well as controlling the introduction and generation of particles and microbial contamination. Understanding the ISO 14644-1 standard is essential for organizations that utilize cleanrooms in sectors like microelectronics, pharmaceuticals, medical devices, and aerospace.

What is the ISO 14644 standard?

ISO 14644 is an international standard that sets the specifications for cleanrooms and associated controlled environments. It consists of multiple parts:

  • ISO 14644-1: Classification of air cleanliness by particle concentration
  • ISO 14644-2: Monitoring to provide evidence of cleanroom performance related to air cleanliness by particle concentration
  • ISO 14644-3: Metrology and test methods
  • ISO 14644-4: Design, construction and start-up
  • ISO 14644-5: Operations
  • ISO 14644-6: Vocabulary
  • ISO 14644-7: Separative devices (clean air hoods, gloveboxes, isolators and mini-environments)
  • ISO 14644-8: Classification of molecular contamination

The ISO 14644-1 standard specifically establishes the classification system for air cleanliness in cleanrooms and clean zones. This allows the specification of cleanroom classes regarding airborne particulates of defined sizes per volume of air. Organizations can then design and construct cleanrooms to meet the air cleanliness classifications based on their contamination control needs.

History of ISO 14644-1

The ISO 14644 standard was developed by the International Organization for Standardization (ISO) Technical Committee (TC) 209. The need for a comprehensive international cleanroom standard was recognized in the early 1990s. At the time, various classifications existed across different countries and industries, resulting in confusion and inconsistency regarding cleanroom specifications and operation.

ISO TC 209 was formed in 1993 to develop the new cleanroom standard. ISO 14644-1, classifying air cleanliness by particle concentration, was published in 1999. It was based on the US Federal Standard 209E – Airborne Particulate Cleanliness Classes in Cleanrooms and Clean Zones, which was then withdrawn in 2001 when ISO 14644-1 took effect.

ISO 14644-1 has been reviewed and confirmed multiple times over the years. The second edition was published in 2015, with minor revisions related to particle counting methods. Work is currently underway on the next review and potential update of ISO 14644-1.

Purpose and Scope of ISO 14644-1

The purpose of ISO 14644-1 is to:

  • Specify the classification of air cleanliness in cleanrooms and clean air devices in terms of concentration of airborne particles
  • Provide a method to demonstrate continued compliance with the specified classification
  • Facilitate consistent specification and interpretation of cleanroom classifications

ISO 14644-1 sets the classification of airborne particulate cleanliness for cleanrooms and clean zones. This includes requirements for the determination of concentrations of airborne particles equal to and larger than specified sizes from 0.1 μm to 5.0 μm.

The ISO 14644-1 standard applies to:

  • Cleanrooms and clean zones for all industries
  • Clean air devices such as clean benches, clean hoods, glove boxes and isolators
  • Temperature controlled environments from Grade 5 to Grade 9 where temperature ranges from 15°C to 30°C

The standard does not specify requirements for controlled environments outside the stated temperature range. It also excludes classification of microbial contamination and concentration limits for specific chemicals or gases.

ISO 14644-1 Cleanroom Classifications

ISO 14644-1 establishes a numerical classification system for air cleanliness in cleanrooms and clean zones based on the concentration of airborne particles. This covers particle sizes ranging from 0.1 μm to 5.0 μm per cubic meter of air.

Cleanroom ISO classifications designated by this standard are:

ISO Class Maximum particles/m3 equal to and above
ISO 1 10 particles of 0.1 μm
ISO 2 100 particles of 0.1 μm
ISO 3 1,000 particles of 0.1 μm
ISO 4 10,000 particles of 0.1 μm
ISO 5 100,000 particles of 0.1 μm
ISO 6 1,000,000 particles of 0.1 μm
ISO 7 352,000 particles of 0.2 μm
ISO 8 3,520,000 particles of 0.3 μm
ISO 9 35,200,000 particles of 0.5 μm

Lower ISO classes indicate cleaner air, since the permitted concentrations of particles is lower. For example, an ISO class 5 cleanroom allows up to 100,000 particles of 0.1 μm per cubic meter of air, while an ISO class 4 cleanroom only allows up to 10,000 particles of the same size.

As particle size increases from 0.1 μm and above, the maximum concentration is specified in a stepped progression. This is because larger particles are more relevant for contamination control in real-world applications. An ISO 5 cleanroom allows 352,000 particles of 0.2 μm per cubic meter, while permitting 100,000 particles of 0.1 μm.

Unidirectional Airflow

For some applications, ISO 14644-1 also defines unidirectional airflow cleanroom classes based on maximum permitted concentration of particles ≥0.5μm in cubic meter:

ISO Class Maximum particles/m3 equal to and above
UDI 1 10 particles ≥ 0.5μm
UDI 2 100 particles ≥ 0.5μm
UDI 3 1,000 particles ≥ 0.5μm
UDI 4 10,000 particles ≥ 0.5μm
UDI 5 100,000 particles ≥ 0.5μm

Unidirectional or laminar airflow is used for more stringent particle control. Air moves in parallel flow with minimal mixing, providing targeted protection of sensitive surfaces.

ISO 14644-1 Requirements

The key requirements specified in ISO 14644-1 for cleanroom classification include:

Sampling and Statistical Limits

Particle concentration sampling must be carried out at representative locations in the cleanroom or clean zone to characterize air cleanliness. Sampling volumes, numbers and locations should be sufficient to provide statistical significance.

The 95% upper confidence limit (UCL) is used to determine if the maximum permitted particle concentration for the specified ISO class is met. At least 3 sample sets should be taken per sampling location.

Particle Counting and Sizing

Counting of airborne particles must use appropriate automatic particle counters that can size and count particles ≥0.1 μm. Sampling flow rates, measurement thresholds and sizing accuracy are specified.

For particles ≥0.5 μm, an optical particle counter (OPC) is required. Condensation nucleus counters (CNC) are needed for particles smaller than 0.5 μm down to 0.1 μm size.

Sampling Locations and Conditions

Sampling locations should represent the ISO class specified for the cleanroom or clean zone. They should be at the particle-generating source, at the work site, along the airflow and at filters or airflow control elements.

Conditions should represent normal operating state in terms of factors like airflow, activity, equipment operation and number of personnel.

Re-classification and Monitoring

Cleanrooms and clean zones should be re-classified at least once per year. Routine particle concentration monitoring is required at key locations to demonstrate continued compliance with specified ISO class limits.

Alert and action particle concentration limits are recommended to trigger increased monitoring or corrective actions. Portable particle counters can allow cost-effective routine monitoring.

Benefits of ISO 14644-1 Standard

Some key benefits of the ISO 14644-1 cleanroom classification standard include:

  • Consistent specifications – Provides recognized international classifications that can be uniformly applied for cleanroom design, construction, operation and control.
  • Measurable criteria – Establishes quantitative particle concentration limits for specified ISO classes that can be measured and monitored.
  • Risk-based classes – Classification scales pegged to particle sizes and concentrations allow matching cleanliness to contamination risks.
  • Industry agnostic – Applicable across pharmaceutical, microelectronics, medical, aerospace and other sectors requiring cleanrooms.
  • Compliance – Meeting the ISO 14644-1 standard can support regulatory compliance and quality system requirements.
  • Global acceptance – As an ISO standard, it is internationally recognized and accepted as representing cleanroom industry best practice.

By providing a consistent basis for classification and control of cleanrooms and clean zones, ISO 14644-1 allows different industries, companies and geographic regions to align on specifications, requirements and operations.

Challenges of Meeting ISO 14644-1

While ISO 14644-1 provides a solid standard for cleanroom classification, operating to meet the requirements can present some challenges, including:

  • Tight limits on particles – Achieving and maintaining very low ISO class limits for small particles can be technically difficult.
  • Personnel and gowning – People generate particles, so gowning, entry and exit protocols must control contamination.
  • Process and equipment – All production equipment must be designed and operated to emit minimal particles.
  • Air filters – High-grade HEPA or ULPA filters are needed recirculate cleanroom air.
  • Facility integrity – The cleanroom structure including walls, doors, seals and fixtures must prevent incursion of unfiltered air.
  • Monitoring – Maintaining ISO class requires routine particle counting and control of excursions.

Significant capital investment and operating diligence is required to build and run cleanrooms to ISO 14644-1 specifications. However, the particle-free environment this makes possible is critical for many advanced manufacturing processes and products.

Cleanroom Design and Construction per ISO 14644-1

To achieve the desired ISO classification, cleanrooms must be properly designed and constructed. Key aspects include:

  • Specifying the required ISO class based on contamination control needs.
  • Defining cleanroom layout and airflow patterns.
  • Selecting suitable air filtration systems.
  • Choosing proper materials and finishes for walls, floors and ceilings.
  • Installing air-tight doors, windows, seals and fixtures.
  • Providing gowning rooms and personnel controls.
  • Equipping with particle monitoring systems.
  • Documenting the construction and qualification process.

Cleanroom design should locate higher ISO Class areas upstream, with lower classes downstream to maintain ascending air cleanliness. Unidirectional or laminar airflow can provide local control at critical equipment.

Materials used must not shed particles. Surfaces should be smooth, non-porous and resistant to damage. Cleanroom-suitable filtration systems include ULPA or HEPA for recirculation, with pre-filters for make-up air.

Qualification testing like air flow visualization and particle mapping helps verify that the installation meets specifications before operation.

Maintaining ISO 14644-1 Compliance

After the cleanroom is constructed and qualified, maintaining continued compliance with ISO 14644-1 particle limits involves:

  • Using approved cleaning methods that minimize particle generation.
  • Implementing access controls and gowning procedures for personnel.
  • Developing SOPs for material handling, waste removal, equipment operation etc.
  • Conducting periodic re-qualification and re-certification.
  • Measuring and recording differential pressure between cleanroom classes.
  • Regular monitoring of airborne particle concentrations.
  • Taking corrective actions if particle limits are exceeded.

Personnel working in the cleanroom must be properly trained to understand contamination risks and control procedures. Monitoring of airborne particles should be conducted in accordance with ISO 14644-2.

If counts rise above established limits, investigation and troubleshooting is required to find and address the source. Filters and airflow may need replacement or repair. Breaches in the facility’s physical integrity must also be identified and fixed.

Conclusion

The ISO 14644-1 standard provides a rigorous, internationally-accepted basis for classification of cleanrooms and associated controlled environments based on airborne particle cleanliness. It establishes maximum concentrations of particles equal or above specified sizes that make up the ISO class numeric designations.

Compliance with ISO 14644-1 requires careful cleanroom design, construction, qualification and disciplined operation and monitoring. However, it enables particle-sensitive industries to achieve the ultra-clean environments necessary for their processes and products.

Given its focus specifically on airborne particle cleanliness, ISO 14644-1 forms part of a broader family of ISO 14644 standards covering other aspects of cleanroom performance and control like air filtration, microbial contamination, sampling methods and separative devices.

Regular review and revision of the standard by ISO technical committees also helps keep ISO 14644-1 up-to-date with technological advances in instrumentation, measurement science and cleanroom best practices.