Cleanrooms are controlled environments designed to minimize the presence of contaminants, such as dust, airborne microbes, and chemical vapors. They play a crucial role in various industries, including pharmaceuticals, biotechnology, electronics, and aerospace.
This article will explore the fundamentals of cleanrooms, their design principles, components, and applications in different industries. We will also discuss the importance of maintaining cleanroom standards and the various protocols and procedures involved in cleanroom operations.
A cleanroom is a specially designed and controlled environment where the concentration of airborne particles is kept to a minimum. The primary purpose of a cleanroom is to prevent contamination of sensitive processes or products, ensuring their quality and safety.
While there are many improvised airborne pathogen purification systems, cleanrooms remain the primary requirement in industries where even the smallest amount of contamination can have significant consequences, such as pharmaceutical manufacturing, semiconductor fabrication, and biotechnology research.
The purpose of cleanrooms is to control contaminants, which involves regulating various factors such as
Air filtration - The use of HEPA and ULPA filters to remove particles to protect sensitive products in critical areas.
Temperature and Humidity Control - Maintaining a consistent environment for optimal product quality and safety.
Pressure - Maintaining a positive pressure to keep contaminants out, ensuring a safe and sterile environment.
The level of cleanliness required in a cleanroom depends on the specific industry and application. For example, in the pharmaceutical industry, cleanrooms prevent contamination of drugs and medical devices, ensuring their sterility and patient safety. Since cleanliness is also a critical regulatory requirement, it’s appropriately addressed in the process of a medical device design.
Recommended Reading: Stages of Medical Device Development: A Comprehensive Guide
In the semiconductor industry, cleanrooms are essential for maintaining the integrity of microelectronic components, as even a single dust particle can cause defects in the semiconductor manufacturing process.
Cleanrooms are classified based on the number and size of airborne particles allowed per unit volume of air. The International Organization for Standardization (ISO) developed the ISO 14644-1 standard, which defines cleanroom classifications and provides guidelines for measuring and testing cleanroom performance. The ISO 14644-1 standard classifies cleanrooms into nine classes, ranging from ISO Class 1 (the cleanest) to ISO Class 9 (the least clean).
Each ISO class has specific limits for the maximum concentration of particles of various sizes. For example, an ISO Class 5 cleanroom must have no more than 3,520 particles of 0.5 micrometers or larger per cubic meter of air, while an ISO Class 7 cleanroom can have up to 352,000 particles of the same size per cubic meter of air. The classification system helps industries determine the appropriate level of cleanliness required for their specific applications and processes.
The following table shows the ISO 14644-1 cleanroom classifications, along with the maximum number of particles permitted per cubic meter of air:
ISO Class
Maximum number of particles per cubic meter (≥ 0.5 µm)
Maximum number of particles per cubic meter (≥ 0.1 µm)
1
10
10
2
100
24
3
1,000
237
4
10,000
2,370
5
100,000
23,700
6
1,000,000
237,000
7
10,000,000
2,370,000
8
100,000,000
23,700,000
9
>100,000,000
>23,700,000
In addition to the ISO standard, other classification systems exist, such as the United States Federal Standard 209E (FS 209E), which was widely used before the adoption of ISO 14644-1. The FS 209E standard classifies cleanrooms into six classes, ranging from Class 1 (the cleanest) to Class 100,000 (the least clean). Although the FS 209E standard has been officially replaced by ISO 14644-1, it is still used as a reference in some industries and regions.
The ISO 14644-1 is one of the most important standards in the modern industries. Therefore, it’s implemented in Industry 4.0. as it provides a framework for ensuring the cleanliness of manufacturing environments.
Further Reading: Benefits of Industry 4.0
The cleanroom classifications help design, construct, and maintain cleanrooms that meet the specific requirements of various industries and applications. Proper classification ensures that cleanrooms provide the necessary level of cleanliness and contamination control, ultimately contributing to the quality and safety of products and processes.
Several key design principles contribute to the effectiveness of a cleanroom in controlling contaminants. These principles include air filtration, air pressure control, and temperature and humidity control.
Air Filtration - One of the most critical aspects of cleanroom design is the air filtration system. High-efficiency particulate air (HEPA) filters and ultra-low particulate air (ULPA) filters are commonly used to remove particles from the air.
Air Pressure Control - Maintaining positive air pressure within the cleanroom is essential to prevent the infiltration of contaminants from the surrounding environment. Positive air pressure means that the air pressure inside the cleanroom is higher than the pressure outside, causing air to flow outward when doors or other openings are present. This outward flow of air helps prevent unfiltered air from entering the cleanroom and reduces the risk of contamination.
Temperature and Humidity Control - Controlling temperature and humidity is crucial for maintaining the stability of processes and products within the cleanroom. Excessive temperature or humidity can lead to condensation, corrosion, or other issues that can compromise the cleanliness of the environment.
Air filtration systems are a critical component of cleanrooms, as they are responsible for removing particles and contaminants from the air. Several types of air filtration systems are used in cleanrooms, including HEPA and ULPA filters, as well as various configurations of air handling units (AHUs).
HEPA Filters - High-efficiency particulate air (HEPA) filters are widely used in cleanrooms because they capture 99.97% of particles 0.3 micrometers in size. HEPA filters are made from a dense network of randomly arranged fibers, typically composed of glass or synthetic materials. As air passes through the filter, particles are trapped by a combination of mechanisms, including interception, impaction, and diffusion.
Fig 1: HEPA Filter for Air Purifier
ULPA Filters - Ultra-low particulate air (ULPA) filters provide an even higher level of filtration than HEPA filters, capturing 99.999% of particles 0.12 micrometers in size. ULPA filters are used in cleanrooms with more stringent cleanliness requirements, such as those found in semiconductor manufacturing or pharmaceutical production. Like HEPA filters, ULPA filters utilize a dense network of fibers to trap particles, but they have a higher filtration efficiency due to their smaller pore size and increased fiber density.
Air Handling Units (AHUs) - AHUs are used in cleanroom air filtration systems to condition and distribute the filtered air throughout the cleanroom. AHUs typically consist of a fan, filter, cooling coil, and heating coil, all housed within a single unit. The AHU draws in air from the surrounding environment, filters it through the HEPA or ULPA filter, and then conditions the air by adjusting its temperature and humidity before distributing it throughout the cleanroom. AHUs can be configured in various ways, such as single-pass or recirculating systems, depending on the specific requirements of the cleanroom.
By utilizing appropriate air filtration systems, cleanrooms can maintain the required level of cleanliness and minimize the risk of contamination, ensuring the quality and safety of products and processes.
Heating, ventilation, and air conditioning (HVAC) systems play a crucial role in maintaining the controlled environment of a cleanroom. HVAC systems are responsible for regulating temperature, humidity, and air pressure, ensuring optimal conditions for the specific industry and application.
Fig 2: A heating and ventilation system in a factory setup
Here is a quick look at the main components of an HVAC system
Temperature Control - Just as valuable as it is in process control, precise temperature control is essential in cleanrooms, as fluctuations in temperature can affect the stability of processes and products. HVAC systems use cooling and heating coils to maintain the desired temperature within the cleanroom, ensuring consistent conditions for sensitive processes.
Humidity Control - Maintaining the appropriate humidity level is also critical in cleanrooms, as excessive humidity can lead to condensation, corrosion, or other issues that can compromise the cleanliness of the environment. On the other hand, low humidity can cause static electricity buildup, which can damage sensitive electronic components. HVAC systems use humidifiers and dehumidifiers to regulate humidity levels, providing the optimal balance for the specific application.
Air Pressure Control - As mentioned earlier, positive air pressure is essential for preventing the infiltration of contaminants from the surrounding environment. HVAC systems help maintain positive air pressure by controlling the volume and velocity of air entering and exiting the cleanroom. This is achieved through the use of fans, dampers, and other components that regulate airflow and pressure.
Air Distribution - Proper air distribution is vital for ensuring uniform cleanliness throughout the cleanroom. HVAC systems use a combination of ductwork, diffusers, and return air grilles to distribute filtered and conditioned air evenly across the cleanroom. This helps maintain consistent cleanliness levels and prevents the buildup of contaminants in specific areas.
The structure and constructional design of cleanrooms are of paramount importance because they directly impact the ability of the cleanroom to meet its intended purpose. Cleanrooms are designed to control contamination, and the structure and construction of the room play a vital role in this.
A well-designed cleanroom will have the following features:
Airtight Enclosure - The cleanroom must be an airtight enclosure to prevent the ingress of contaminated air.
HEPA filtration - The cleanroom must be equipped with high-efficiency particulate air (HEPA) filters to remove airborne contaminants.
Positive Pressurization - The cleanroom must be maintained at a positive pressure relative to the surrounding environment.
Unidirectional Airflow - The cleanroom must have unidirectional airflow, which means that the air flows in one direction only.
There are two primary types of cleanroom construction: modular and conventional. Each type has its advantages and disadvantages, depending on the industry's specific requirements and application.
These are pre-fabricated, self-contained units that can be easily assembled, disassembled, and reconfigured. They are typically constructed from lightweight materials, such as aluminum, steel, or plastic, and are designed to be easily transported and installed. Some of the advantages of modular cleanrooms include:
Flexibility - Modular cleanrooms can be easily expanded, downsized, or reconfigured to accommodate changing needs or requirements.
Construction Speed - Modular cleanrooms can be assembled more quickly than conventional cleanrooms, reducing downtime and allowing for faster project completion.
Cost-effectiveness - Modular cleanrooms often have lower construction costs than conventional cleanrooms, requiring less labor and materials.
Disadvantage of Modular Cleanrooms - These rooms offer reduced structural stability and a potentially shorter lifespan compared to conventional cleanrooms.
These are built using traditional construction methods and materials like concrete, steel, and drywall. They are typically more permanent structures and are designed to meet specific industry standards and requirements. Some advantages of conventional cleanrooms include:
Durability - Conventional cleanrooms are generally more robust and have a longer lifespan than modular cleanrooms.
Customization - Conventional cleanrooms can be designed and built to meet the unique requirements of a specific industry or application, allowing for greater customization and optimization.
Disadvantage of Conventional Cleanrooms - These rooms can be more expensive and time-consuming to construct compared to modular cleanrooms, and they may be less flexible in terms of expansion or reconfiguration.
Cleanroom flooring and wall systems are essential components of cleanroom design, as they contribute to maintaining cleanliness and preventing contamination. The choice of materials and construction methods for flooring and wall systems can significantly impact a cleanroom's overall performance and effectiveness.
Cleanroom flooring must be durable, easy to clean, and resistant to chemicals and abrasion. Common flooring materials used in cleanrooms include:
Epoxy - Epoxy flooring is a popular choice for cleanrooms due to its seamless, non-porous surface, which is easy to clean and resistant to chemicals. Epoxy flooring can also be formulated with anti-static properties to reduce the risk of electrostatic discharge (ESD) in sensitive environments.
Fig 3: A cleanroom featuring an Epoxy System Flooring and double glass windows
Vinyl - Vinyl flooring is another common option for cleanrooms, as it is cost-effective, easy to maintain, and available in a variety of colors and finishes. Vinyl flooring can also be made with anti-static properties for ESD-sensitive applications.
Raised access flooring - Raised access flooring systems consist of modular panels supported by adjustable pedestals, creating a space beneath the floor for routing utilities, such as electrical and HVAC systems.
Cleanroom walls must be constructed from materials that are easy to clean, resistant to chemicals, and capable of maintaining airtight seals. Common wall systems used in cleanrooms include:
Modular Wall Panels - These are pre-fabricated, interlocking panels made from materials such as aluminum, steel, or plastic. They are easy to install, reconfigure, and maintain, making them a popular choice for cleanroom construction. Modular wall panels can also be designed with integrated windows, doors, and utility ports for added convenience.
Gypsum Board - Also known as drywall, is a conventional wall construction material that can be used in cleanrooms when properly sealed and finished. Gypsum board walls must be coated with a suitable paint or sealant to create a smooth, non-porous surface that is easy to clean and resistant to chemicals.
Glass or acrylic walls - Glass or acrylic walls can be used in cleanrooms to create a visually open environment while maintaining airtight seals and cleanliness. Glass and acrylic walls are easy to clean and resistant to chemicals, making them suitable for cleanroom applications.
Maintaining the cleanliness and integrity of a cleanroom environment requires strict adherence to protocols and procedures. These guidelines help ensure that cleanroom personnel, equipment, and processes do not introduce contaminants that could compromise product quality or safety.
Some of the key aspects of cleanroom protocols and procedures include:
Personnel Training - Cleanroom personnel must be trained in proper cleanroom etiquette, including gowning procedures, hygiene practices, and handling materials and equipment. This training helps minimize the risk of contamination introduced by human activity, as people are a significant source of particles and contaminants in cleanrooms.
Gowning Procedures - Cleanroom personnel must wear specialized clothing, such as coveralls, gloves, face masks, and shoe covers, to minimize the release of particles from their bodies and clothing. Gowning procedures typically involve donning cleanroom garments in a designated gowning area, following a specific sequence to minimize contamination.
Material and Equipment Handling - Materials and equipment entering the cleanroom must be carefully handled to prevent contamination. This may involve cleaning or sterilizing items before entering the cleanroom, using specialized containers or packaging, and following specific procedures for moving items.
Access Control - Access to cleanrooms should be restricted to authorized personnel who have received proper training in cleanroom protocols and procedures. Access control measures, such as keycards or biometric systems, can help ensure that only trained personnel enter the cleanroom, reducing the risk of contamination.
Regular cleaning and disinfection of cleanroom surfaces, equipment, and tools are essential for maintaining cleanliness and preventing the buildup of contaminants. Effective cleaning and disinfection procedures involve the use of specialized cleaning agents, equipment, and techniques tailored to the specific requirements of the cleanroom environment.
Cleaning Agents - Cleanroom-grade cleaning agents are designed to remove particles, residues, and contaminants from surfaces without introducing additional contaminants. These cleaning agents may include detergents, disinfectants, and sterilants, depending on the specific needs of the cleanroom. It is crucial to select cleaning agents compatible with the materials and surfaces in the cleanroom to avoid damage or degradation.
Cleaning Techniques - Effective cleanroom cleaning and disinfection procedures involve specific techniques to ensure thorough removal of contaminants. Some common cleanroom cleaning techniques include:
Wiping - Using a systematic and consistent pattern, wiping surfaces with cleanroom-grade wipes helps ensure that contaminants are effectively removed. Wipes should be folded and rotated to expose a clean surface as they become soiled, minimizing the risk of recontamination.
Mopping - Mopping cleanroom floors, walls, and ceilings should follow a specific pattern, such as starting from the cleanest area and moving towards the dirtiest, to prevent the spread of contaminants. Mop heads should be changed regularly to maintain cleanliness.
Vacuuming - Vacuuming should be performed using cleanroom-grade vacuum cleaners with HEPA or ULPA filters, ensuring that particles are captured and not released back into the environment. Vacuuming should be done systematically, covering all surfaces and areas within the cleanroom.
By implementing effective cleaning and disinfection procedures, cleanrooms can maintain the required cleanliness and contamination control level, ensuring the quality and safety of products and processes.
Monitoring and validation are essential aspects of cleanroom operations and maintenance, as they help ensure that the cleanroom performs as intended and meets the required cleanliness standards. Regular testing and certification are necessary to maintain compliance with industry regulations and guidelines.
Particle Count Monitoring - This is a critical aspect of cleanroom validation, as it measures the concentration of airborne particles within the cleanroom environment. Particle counters are used to sample the air at various locations within the cleanroom, providing real-time data on particle concentrations. This information is used to assess the performance of the cleanroom's air filtration system and identify any potential issues or areas of concern.
Airflow and Pressure Monitoring - Monitoring the airflow and pressure within the cleanroom is essential for maintaining proper air circulation and positive pressure. Sensors and gauges are used to measure air velocity, pressure differentials, and other parameters, ensuring that the cleanroom's HVAC system functions correctly and maintains the required conditions.
Temperature and Humidity Monitoring - Temperature and humidity sensors are used to continuously monitor the environmental conditions within the cleanroom, ensuring that they remain within the specified ranges. This data is essential for maintaining the stability of processes and products and preventing issues related to condensation, corrosion, or static electricity.
Recommended Reading: How to Select the Best Temperature Sensors for Your Smart Project
Microbiological Monitoring - In cleanrooms used for pharmaceutical, biotechnology, or other life science applications, microbiological monitoring is necessary to detect the presence of microorganisms, such as bacteria, fungi, or viruses. This monitoring typically involves the use of air samplers, surface swabs, or contact plates to collect samples, which are then analyzed in a laboratory to identify and quantify any microbial contaminants.
Certification and Compliance - Cleanrooms must undergo regular testing and certification to ensure compliance with industry standards and regulations, such as ISO 14644-1 or the United States Federal Standard 209E.
Leakage Detection - Leaks can allow contaminated air to enter the cleanroom, compromising the quality of products being produced and putting employees at risk. Therefore, Cleanroom maintenance personnel regularly inspect the cleanroom for leaks and perform leakage detection tests on key areas.
Fig 4: Leakage Scan on a HEPA filter in a cleanroom
Leakage detection in cleanrooms can be conducted using a variety of methods, depending on the specific application and the type of leak being detected. Some of the most common methods include:
Aerosol Photometer - This device measures the concentration of airborne particles in the air. An increase in particle concentration can indicate a leak.
Sniffer Probe - This device is used to detect the presence of tracer gas that has been released into the cleanroom.
Ionization Chamber - This device detects the presence of ions in the air. An increase in ion concentration can indicate a leak. Ionization chambers are typically used to detect leaks in vacuum systems and other high-purity environments.
Pressure Decay Test - This test measures the rate at which the pressure in a sealed enclosure decreases over time. These tests are typically used to detect leaks in large enclosures, such as cleanroom chambers and gloveboxes.
Bubble Leak Test - This test uses a soapy solution to identify leaks in pressurized systems. If the soapy solution bubbles when applied to a joint or fitting, it indicates a leak. Bubble leak tests are typically used to detect leaks in plumbing, gas lines, and other pressurized systems.
Cleanrooms play a vital role in the pharmaceutical and biotechnology industries, where maintaining a contamination-free environment is crucial for ensuring product quality, safety, and efficacy. These industries use cleanrooms for various purposes, such as research and development, manufacturing, and quality control.
Research and Development - In pharmaceutical and biotechnology research, cleanrooms provide a controlled environment for conducting experiments and studies involving sensitive biological materials, such as cells, tissues, or microorganisms. Maintaining a clean and sterile environment is essential for preventing contamination and ensuring the accuracy and reliability of research results.
Manufacturing - Cleanrooms are used in manufacturing pharmaceutical products, such as drugs, vaccines, and medical devices, to ensure sterility and patient safety. The manufacturing process often involves handling active pharmaceutical ingredients (APIs), which must be protected from contamination to maintain their potency and effectiveness. Cleanrooms in pharmaceutical manufacturing are typically designed to meet stringent cleanliness standards, such as ISO Class 5 or higher, depending on the specific product and process requirements.
Quality Control - Quality control is a critical aspect of pharmaceutical and biotechnology production, as it helps ensure that products meet the required specifications and regulatory standards. Cleanrooms are used for various quality control activities, such as microbiological testing, environmental monitoring, and product inspection. These activities require a controlled environment to prevent contamination and ensure the accuracy and reliability of test results.
Cleanrooms are essential in the electronics and semiconductor manufacturing industries, where even the smallest amount of contamination can have significant consequences on product quality and performance. These industries use cleanrooms for various processes, such as wafer fabrication, assembly, and testing.
Fig 5: A view of a Bright Advanced Semiconductor Production Fab Cleanroom with Working Overhead Wafer Transfer System
Wafer Fabrication - The fabrication of semiconductor wafers involves numerous processes, such as photolithography, etching, and deposition, which require a contamination-free environment to ensure the integrity of the microelectronic components. Cleanrooms used in wafer fabrication are typically designed to meet stringent cleanliness standards, such as ISO Class 3 or higher, to minimize the risk of defects caused by particles or contaminants.
Assembly and Packaging - Semiconductor devices are assembled and packaged after wafer fabrication to protect them from environmental factors and facilitate their integration into electronic systems. Cleanrooms used in assembly and packaging processes must maintain a controlled environment to prevent contamination that could compromise the performance or reliability of the devices. These cleanrooms are typically designed to meet cleanliness standards such as ISO Class 5 or higher, depending on the specific requirements of the product and process.
Testing and Quality Control - Semiconductor devices undergo various testing and quality control procedures to ensure their performance, reliability, and compliance with industry standards. Cleanrooms used for testing and quality control must provide a controlled environment that minimizes contamination risk, ensuring test results' accuracy and reliability.
Cleanrooms play a critical role in the aerospace and defense industries, where maintaining a contamination-free environment is essential for ensuring the quality, reliability, and safety of products and systems.
In these industries, cleanrooms are used for various purposes, such as manufacturing sensitive components, assembling spacecraft and satellites, and testing advanced technologies.
Sensitive Component Manufacturing - Aerospace and defense applications often involve the use of sensitive components, such as sensors, optics, and microelectronic devices, which require a controlled environment during manufacturing to prevent contamination and ensure their performance and reliability. Depending on the product and process requirements, cleanrooms used in the manufacturing of sensitive components must meet specific cleanliness standards, such as ISO Class 5 or higher.
Recommended Reading: Aerospace manufacturing in 2023
Spacecraft and Satellite Assembly - The assembly of spacecraft and satellites involves the integration of various components and systems, which must be protected from contamination to ensure their functionality and longevity in the harsh conditions of space. Cleanrooms used for spacecraft and satellite assembly must maintain a controlled environment that minimizes the risk of contamination, typically meeting cleanliness standards such as ISO Class 6 or higher.
Testing and Quality Control - Aerospace and defense products and systems undergo rigorous testing and quality control procedures to ensure their performance, reliability, and compliance with industry standards and regulations. Cleanrooms used for testing and quality control must provide a controlled environment that minimizes contamination risk, ensuring test results' accuracy and reliability. The cleanliness standards for these cleanrooms depend on the specific testing procedures and product requirements.
Cleanrooms are essential in various industries, including pharmaceuticals, biotechnology, electronics, and aerospace, where maintaining a contamination-free environment is crucial for ensuring product quality, safety, and reliability. By adhering to strict design principles, using appropriate components and equipment, and following rigorous protocols and procedures, cleanrooms can effectively control contaminants and provide the necessary level of cleanliness for diverse applications. Regular monitoring and validation are vital for maintaining compliance with industry standards and regulations, ensuring cleanroom environments' ongoing performance and effectiveness.
A cleanroom is a controlled environment designed to minimize the presence of contaminants, such as dust, airborne microbes, and chemical vapors. Cleanrooms are essential in industries where even the smallest amount of contamination can have significant consequences, such as pharmaceutical manufacturing, semiconductor fabrication, and biotechnology research.
Cleanrooms are classified based on the number and size of airborne particles allowed per unit volume of air. The International Organization for Standardization (ISO) developed the ISO 14644-1 standard, which defines cleanroom classifications and provides guidelines for measuring and testing cleanroom performance.
The key design principles of cleanrooms include air filtration, air pressure control, and temperature and humidity control. These principles help maintain a controlled environment that minimizes the risk of contamination.
The main components of a cleanroom include air filtration systems, HVAC systems, and cleanroom furniture and fixtures. These components work together to maintain the required level of cleanliness and contamination control.
Monitoring and validation are essential aspects of cleanroom operations and maintenance, as they help ensure that the cleanroom performs as intended and meets the required cleanliness standards. Regular testing and certification are necessary to maintain compliance with industry regulations and guidelines.
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