Cleanrooms are controlled environments with extremely low levels of pollutants and contaminants used in manufacturing, scientific research, and other processes that require highly clean environments. The International Organization for Standardization (ISO) has developed a set of standards for classifying and controlling cleanrooms based on the concentration of particles per volume of air. These ISO standards help define cleanroom design, air filtration, materials, apparel, and operations.
ISO standards classify cleanrooms into numbered ISO classes from 1 to 9, with ISO 1 representing the cleanest environments and ISO 9 representing the least clean. These classes specify the maximum allowable concentration of particles of defined sizes per volume of air. For example, an ISO class 5 cleanroom allows no more than 3,520 particles of 0.5 μm or larger per cubic meter of air. Lower ISO classes require exponentially greater air filtration and cleaning procedures to meet the stringent particle concentration requirements.
Background on ISO Standards
The ISO 14644 cleanroom standards originally emerged from the US Federal Standard 209E Airborne Particulate Cleanliness Classes in Cleanrooms and Clean Zones. The ISO Technical Committee 209 working group was formed in 1993 to develop a unified international standard for cleanroom classifications and testing methods. This led to the publication of ISO 14644-1 in 1999, which established air cleanliness classifications based on maximum concentrations of particles per volume of air.
ISO 14644-1 covers the classification of air cleanliness in cleanrooms and associated controlled environments. Classification is based on the concentration of airborne particles measured under specified conditions. The standard aims to establish a consistent basis for comparing cleanroom classifications between different facilities globally [1]. It provides a means of specifying and testing cleanrooms to control contamination and ensure products meet quality standards.
The purpose of the ISO 14644 standards is to provide globally recognized specifications for cleanroom design, construction, and operation. They aim to improve efficiency, environmental control, product quality, and yield in industries where contamination control is critical like electronics, pharmaceuticals, medical devices, and aerospace [2].
Cleanroom Classifications
The International Organization for Standardization (ISO) provides a classification system for cleanrooms based on the concentration of particles per cubic meter of air of certain sizes. The ISO 14644-1 standard defines cleanroom classes ISO 1 through ISO 9, with ISO 1 having the lowest maximum concentrations of particles and ISO 9 having the highest allowable levels.
The key particle sizes measured are ≥0.1 μm, ≥0.2 μm, ≥0.3 μm, ≥0.5 μm, and ≥5.0 μm. For example, an ISO class 5 cleanroom must have less than 3,520 particles per cubic meter that are ≥0.5 μm in size. Here are the maximum particle concentration limits for the ISO 1-9 cleanroom classifications (Source):
- ISO 1: 10 particles/m3 for ≥0.1 μm particles
- ISO 2: 100 particles/m3 for ≥0.2 μm particles
- ISO 3: 1,000 particles/m3 for ≥0.3 μm particles
- ISO 4: 10,000 particles/m3 for ≥0.5 μm particles
- ISO 5: 100,000 particles/m3 for ≥0.5 μm particles
- ISO 6: 1,000,000 particles/m3 for ≥0.5 μm particles
- ISO 7: 352,000 particles/m3 for ≥0.5 μm particles
- ISO 8: 3,520,000 particles/m3 for ≥0.5 μm particles
- ISO 9: 35,200,000 particles/m3 for ≥0.5 μm particles
The standards help define cleanliness levels for different industries and applications. Lower ISO classes like 1-3 are used for pharmaceutical manufacturing, while higher classes like 7-9 may be used for medical device assembly or hospital pharmacies.
ISO Class 8 Specifications
ISO Class 8 cleanrooms, also known as Class 100,000 cleanrooms, are designed to maintain extremely low levels of airborne particles. According to ISO 14644-1 standards, an ISO Class 8 cleanroom must meet the following specifications:
Maximum concentration of ≥0.5 μm particles: 352,000 particles per cubic meter of air (100,000 particles per cubic foot). This sets the limit for the number of allowable 0.5 micron and larger particles per volume of air.
Minimum air changes per hour: 20 air changes per hour of HEPA-filtered air. This ensures consistent filtering and removal of particles from the cleanroom environment.
Typical uses for ISO Class 8 cleanrooms include pharmaceutical powder filling, medical device assembly, aerospace manufacturing, and other applications requiring a moderately clean production area with tightly controlled air quality. The lower particle limits help protect sensitive processes from contamination while still allowing operators to directly access the workspace.
Maintaining an ISO Class 8 environment requires careful monitoring of air filtration systems, proper gowning procedures, and rigorous cleaning protocols. Any breach of the cleanroom could allow excess particles to enter from outside the filtration system.
Measuring Particle Concentration
Particle concentration in cleanrooms is measured using specialized equipment called particle counters. Particle counters use a light source and a photo detector to count and size particles as they pass through a sampling volume. The most common technology used is laser-based light scattering. A laser beam is directed through the sample volume and particles passing through scatter light, which is measured by the detector. The intensity of the scattered light is proportional to the particle size.
Particle counters for cleanroom monitoring are designed to detect particles down to 0.1 μm in size. They actively pull an air sample into the detector using a small vacuum pump. The sample volume, typically 1 ft3 (28.3 liters), is measured precisely using a mass flow sensor. Results are reported in particle concentration per volume of air, such as particles/ft3 or particles/m3. Common cleanroom particle count targets are ≤3520 particles/m3 for ISO Class 5 and ≤352 particles/m3 for ISO Class 6.
In addition to standalone particle counters, automated monitoring systems are often used in cleanrooms. These systems consist of a network of particle counters connected to a central computer. They allow 24/7 monitoring with data logging, alarms, and remote access capabilities (Source). Handheld particle counters are also available for spot-checking problem areas.
Proper calibration and maintenance is critical for accurate particle counting. Counters should be calibrated annually using polystyrene latex spheres of a known size. Regular filter changes, leak checks, and flow audits help ensure optimal performance.
Maintaining ISO Class 8
Maintaining an ISO Class 8 cleanroom environment requires careful control and monitoring of parameters like filtration, gowning procedures, and cleaning protocols. Proper filtration is crucial, requiring the use of HEPA filters that can capture particles as small as 0.3 microns with 99.97% efficiency (American Cleanrooms). Air changes per hour are also monitored, with ISO Class 8 cleanrooms requiring between 30 to 50 air changes per hour (ISOCleanroom).
Personnel gowning procedures help minimize contamination from people entering the cleanroom. Workers pass through an air shower to dislodge particles, put on protective coveralls, masks, gloves, and booties, and take care not to introduce dirt or lint (Cleanroom Technology). Gowning standards aim to reduce human-generated particle counts.
Frequent and thorough cleaning is essential. Surfaces are wiped down daily with deionized water, detergents, or disinfectants like isopropanol or hydrogen peroxide. Floors may be mopped with purified water and sticky mats trap dirt at entrances. Any tools or equipment brought into the cleanroom are cleaned first. Monitoring particulate counts ensures cleaning protocols are effective (American Cleanrooms).
Applications of ISO Class 8
ISO Class 8 cleanrooms are commonly used in industries that require high levels of contamination control, such as:
Semiconductors – During semiconductor manufacturing, airborne particles can cause defects on wafers and reduce yields. ISO Class 8 cleanrooms help minimize contaminants during critical production steps.
Pharmaceuticals – Sterile pharmaceutical products like injectables and ophthalmics require ISO Class 7-8 cleanrooms. Lower grade ISO Class 8 environments may be used for less critical formulation and packaging steps.
Aerospace – Sensitive aerospace components and spacecraft assembly occurs in ISO Class 8 cleanrooms. Strict particulate and microbial control prevents defects and damage.
In these industries, the low particulates in an ISO Class 8 cleanroom helps reduce contamination from the manufacturing environment. Maintaining proper air filtration, airflow patterns, pressure differentials, and gowning procedures is critical for keeping specifications.
Sources:
https://www.cleanroomsbyunited.com/modular-cleanrooms/class-100000-cleanrooms
https://www.americancleanrooms.com/what-is-iso-8-cleanroom-classification/
Designing ISO Class 8 Cleanrooms
When designing an ISO Class 8 cleanroom, careful consideration must be given to the layout, materials used, and air filtration system.
Cleanrooms are typically designed with a modular layout using wall and ceiling panels. These panels must be smooth, non-shedding, and non-porous. Common materials used are vinyl, epoxy coated galvanized steel, and phenolic resin panels (source).
High efficiency particulate air (HEPA) filters are critical for maintaining air cleanliness. ISO Class 8 cleanrooms require HEPA filters with 99.97% efficiency for particles ≥0.3 μm. Air exchanges of at least 100-120 per hour are recommended.
Air enters from the ceiling and returns through low sidewall grilles near the floor. This unidirectional airflow helps sweep particles down and out of the cleanroom (source). Maintaining constant air velocity is key.
Proper cleanroom design minimizes contamination by people, processes, facilities, and equipment within the controlled space.
Cleaning and Disinfection
Proper cleaning and disinfection procedures are critical for maintaining ISO Class 8 cleanroom standards. Cleanrooms should have detailed protocols specifying cleaning tasks, frequencies, approved chemicals, and procedures.
Typical cleanroom cleaning tasks include vacuuming floors, mopping with purified water, wiping down walls and ceilings, and disinfecting tools and equipment. Cleaning should occur daily before production shifts start. More comprehensive monthly cleanings tackle ceilings, lights, and HVAC systems.
Only contamination-free purified water and approved disinfectants like isopropyl alcohol should be used for cleaning. Tools include HEPA vacuums, squeegees, purified water, cleanroom wipes, sticky mats, and more. Strict gowning and hand washing procedures must be followed to avoid recontamination.
Detailed logs documenting cleaning activities, staff, and verification testing results should be maintained. Successful cleaning keeps particulate and microbial contamination under control.
Conclusion
Particle concentration standards for cleanrooms are crucial for ensuring product quality and process control across a range of industries including pharmaceuticals, medical devices, microelectronics, optics, aerospace, and food manufacturing. Maintaining ISO Class 8, with its stringent maximum of 3,520,000 particles per cubic meter of ≥0.5 μm diameter, helps prevent contamination and defects in sensitive processes and products.
Meeting the particle count requirements for ISO 8 cleanrooms requires careful monitoring, filtration, HVAC design, cleaning protocols, personnel practices, and facility maintenance. Investing in proper cleanroom design, construction, and operation provides significant returns by minimizing risks to products, personnel, and processes. As technology progresses, particle concentration standards will likely continue advancing to enable increasingly sophisticated manufacturing in contamination-controlled environments.
In summary, the meticulous cleanliness standards defined by classifications like ISO 8 reflect the growing need for spotless production environments. Controlling airborne particulates facilitates scientific research, medical therapies, microtechnology, and other innovative products that enhance quality of life around the world.