A Comprehensive Overview of Cleanroom Classes and Standards


Clean rooms have become crucial components for many industries where contamination control is imperative. Whether manufacturing pharmaceuticals, medical devices, aerospace components, or computer chips, clean rooms allow businesses to create their products under tightly regulated cleanliness standards.

In this article, we will explore the different types of cleanroom classifications and the standards that facilities must adhere to in order to maintain their sterile environments.

What Is a Cleanroom?

As per DataHorizzon Research, the Healthcare Cleanroom Consumables Market reached a value of USD 7.2 Billion in 2022. The market is anticipated to grow, reaching a size of USD 12.1 Billion by 2032, exhibiting a Compound Annual Growth Rate (CAGR) of 5.4%.

But what exactly are cleanrooms?

Cleanrooms maintain positive pressure relative to the surrounding factory environment to prevent the infiltration of contaminated air. Various zones within the cleanroom are subject to different levels of differential pressure monitoring.

For instance, the change room is kept at a slightly lower pressure than the cleanroom but is still positively pressurized about the factory. Additionally, service cores within the cleanroom typically sustain negative pressure concerning the process areas.

To achieve and sustain a specific cleanliness classification, cleanrooms are supplied with a continuous stream of air that undergoes HEPA filtration. This meticulous process ensures airborne particles’ controlled concentration and size per cubic meter within the cleanroom environment.

Customizable hard wall cleanrooms offer flexibility in dimensions and can incorporate unique features to meet specific performance criteria. In contrast to traditional drywall-constructed cleanrooms, modular cleanrooms provide a higher degree of design adaptability.

Biotechnology, pharmaceuticals, microelectronics, medical devices, aerospace, e-liquid, cosmetic packaging, USP compounding, printing rooms, GMP rooms, and beverage/bottling rooms frequently benefit from prefabricated cleanrooms.

These industries rely on cleanrooms to uphold stringent environmental controls, safeguarding the quality and integrity of their products and processes.

Cleanroom Classifications

The cleanliness level of a cleanroom, often referred to as its ISO Class, is determined by the concentration of airborne particles with a diameter greater than 0.5 µm per cubic meter.

A cleanroom’s architecture and design are essential to creating a contaminant-free environment. The use of non-particulate materials and stringent construction standards significantly influences the cleanliness level of the space.

For instance, a cleanroom may be classified as ISO 5 if it meets the requirement of fewer than 100 particles per square meter. However, it is essential to recognize the distinction between particles of different sizes, particularly 0.5 microns and 5 microns.

ISO 14644-1 Cleanroom Standards

The ISO 14644-1 cleanroom standards provide a hierarchy of nine classes based on the highest quantity and size of particles per cubic meter.

The classifications range from Class 1, denoting the utmost level of cleanliness with the minimal number of particulates, to Class 9, representing the lowest level of cleanliness with the highest permissible quantity of particles in the air.

ISO Class 1

ISO Class 1 cleanrooms represent an exceptionally exclusive category, with only a limited number of such facilities existing worldwide. The construction of a new ISO 1 cleanroom is not just a routine event. It can be a newsworthy milestone for an organization. These cleanrooms are reserved for highly specialized tasks that demand the utmost in pristine conditions.

An illustrative example of the application of ISO 1 cleanrooms is found in the European Space Agency, which employs such a facility for critical procedures like examining temperature sensors destined for the challenging environment of Mars’ surface. This underlines the significance of ISO 1 cleanrooms in handling tasks of the highest precision and sensitivity.

ISO Class 2

ISO 2 cleanrooms set exacting standards with a maximum allowable limit of 100 particles (0.1 μm) per cubic meter.

Sustaining an average airflow velocity of 0.305–0.457 meters/second and requiring 360–540 air changes per hour, these cleanrooms demand precise control. With Fan/Filter Unit (FFU) coverage of 60–100% and mandatory ULPA filters, ISO 2 cleanrooms ensure stringent particle removal.

Ongoing monitoring, including semiannual particle count tests and annual assessments of airflow and air-pressure differentials, is crucial for maintaining the ultra-clean conditions necessary for tasks demanding meticulous precision.

ISO Class 3

ISO Class 3 cleanrooms adhere to specific cleanliness standards with a maximum allowance of 1,000 particles under 0.1 µm per cubic meter of air. In these controlled environments, up to eight particles sized 1 µm are permitted, while particles larger than 1 µm are strictly prohibited.

This classification underscores the meticulous control required to maintain a clean and particle-free atmosphere, making ISO Class 3 cleanrooms suitable for tasks demanding a high degree of precision and cleanliness.

ISO Class 4

A certain amount of flexibility is provided by ISO Class 4 cleanrooms, which can accommodate up to 10,000 of the lowest measurable particles per cubic meter. Although the classification maintains rigorous limitations, preventing any particle larger than 1 µm, further counts of greater sizes are permitted.

Within this environment, a maximum of 83 particles of size 1 µm are accepted. This balance between flexibility and precision makes ISO Class 4 cleanrooms suitable for tasks where controlled cleanliness is essential but with slightly broader allowances for particle presence.

ISO Class 5

Compared to Class 3 or Class 4, ISO Class 5 cleanrooms allow for greater particle counts: up to 832 particles smaller than 1 µm and up to 29 particles smaller than 5 µm per cubic meter are allowed. Up to 100,000 particles smaller than 0.1 µm are also permitted under this classification.

ISO Class 5 cleanrooms find application in Grade A production, a classification often mandated for aseptic preparation and filling processes. The controlled particle allowance in Class 5 cleanrooms aligns with the meticulous requirements of industries where precision and cleanliness are paramount.

ISO Class 6

ISO Class 6 cleanrooms provide controlled environments allowing particles of all six size classifications. These cleanrooms allow up to 1,000,000 particles smaller than 0.1 µm per cubic meter of air while also allowing a maximum of 293 particles at or under 5 µm.

This classification strikes a balance between controlled cleanliness and broader particle allowances, making ISO Class 6 cleanrooms suitable for applications where a controlled environment is essential but with a slightly more permissive approach to particle presence.

ISO Class 7

As per American Cleanroom Systems, ISO Class 7 cleanrooms represent a medium level of precision in cleanroom classifications, allowing up to 352,000 particles at or under 0.5 µm and up to 2,930 particles less than 5 µm per cubic meter.

Operating under the Grade C classification, these cleanrooms may have up to 3,500,000 particles smaller than 0.5 µm present during operation.

Commonly employed in pharmaceutical applications, ISO-7 cleanrooms follow the ISO cleanroom standards established by the International Organization for Standardization (ISO), providing a framework for various industries, excluding semiconductor applications.

In the United States, this classification is primarily utilized for pharmaceutical, medical devices, biotech, life science, and USP 797 or 800 compounding cleanrooms.

ISO-7 cleanrooms have stringent requirements, necessitating 60 air changes of HEPA-filtered air per hour. These cleanrooms also maintain a particle count of fewer than 2,930 particles per cubic meter, specifically particles equal to or greater than 5 microns in size. In contrast, a typical conditioned office space exhibits over 100 times more particles per cubic meter.

ISO Class 8

ISO-8 cleanrooms adhere to stringent environmental standards, maintaining controlled conditions. These specifications include 20 air changes per hour of HEPA-filtered air and a particle count of less than 29,300 particles per cubic meter that are equal to or greater than 5 microns in size.

This classification ensures a suitable level of cleanliness for various applications. To provide perspective, a conditioned office space, considered a non-cleanroom environment, would typically have over ten times more particles per cubic meter.

ISO-8 cleanrooms play a vital role in applications where controlled cleanliness is essential, striking a balance between precision and practicality.

ISO Class 9

ISO-9 cleanrooms align closely with the characteristics of normal room air. These environments are sampled and known to allow for up to 35,200,000 0.5 micron particles, 8,320,000 1 micron particles, and 293,000 5 micron particles.

In contrast to the highly controlled conditions of lower ISO classes, ISO-9 cleanrooms resemble standard room air conditions. These spaces find application in situations where a less stringent level of cleanliness is acceptable, striking a balance between practicality and controlled environmental conditions.

To wrap it up, cleanrooms, defined by ISO classes, maintain specific cleanliness levels through controlled environments. The ISO 14644-1 standards categorize cleanrooms based on particle concentration. From the exclusive ISO Class 1, used for highly specialized tasks like space exploration, to ISO Class 9, resembling normal room air, each class has defined particle limits.

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