A Guide to Cleanroom Classifications & Standards


Liberty Industries specializes in the manufacturing and distribution of cleanrooms. Our company has been providing high-quality cleanrooms and contamination control materials for over 65 years. Our services are comprehensive, and our engineers can help select or design everything from a complete cleanroom to an individual fan filter unit or packaging materials. We specialize in custom cleanrooms that fit the needs of any industry or facility type, while adhering to the cleanroom classifications and standards.

Cleanrooms create controlled environments free from dust, microorganisms, and other harmful contaminants. The environment’s temperature, pressure, and other relevant environmental factors are completely controlled. Cleanrooms typically have intermediate areas and equipment such as gowning rooms, air showers, and storage areas.

Cleanrooms are held to strict international standards, so it’s important to work with an experienced company that offers both design and construction services. Working with one vendor reduces the risk of oversights, mistakes, incompatibilities, and gaps. Do-It-Yourself jobs or acquiring services from disconnected vendors can leave you with a cleanroom that underperforms, requires frequent repairs, or doesn’t meet your facility’s needs.

Liberty Industries is a leading provider of comprehensive cleanroom solutions. We ensure that your facility receives a cleanroom that meets all of your operational needs while respecting your budget constraints.

This paper will discuss the classification systems cleanrooms must follow to help readers make informed decisions about their cleanroom projects.

infographic cleanroom standards

What Are the Classifications for Cleanrooms?

Before you select a final model or start constructing your cleanroom, it’s important to understand your facility cleanliness requirements.   Different industries operate under levels of cleanliness; often even different applications in the same industry are subject to levels of cleanliness.   The cleanroom classifications can vary depending on the facilities specific cleanliness level requirements.

Some of the industries that require cleanrooms include:

  • Aerospace
  • Electronic part production
  • Manufacturers
  • Medical laboratories
  • Pharmaceutical companies
  • Research facilities

Determine the cleanroom’s size or cleanliness level first so you can locate and follow the appropriate standards and requirements. Taking this crucial first step eliminates the risk of building an incorrect cleanroom or needing to make costly adjustments later.

What is Cleanroom Classification?

Every cleanroom still has some small amount of contaminants. Cleanroom classifications rate the cleanroom based on the number and size of the contaminants in the space.

Cleanroom classifications and standards have different tiers or rankings. For example, The International Standards Organization (ISO) has established cleanroom classification standards that rate cleanrooms from Class 1, which is the most sanitary, to Class 9. A Class 1 cleanroom has much fewer particles per cubic meter than Class 9 rooms.

Particle size matters just as much as particle number. Cleanroom particles are generally measured in microns, and different industries need different levels of separation from larger contaminants. The ISO standards have strict allowances for particles sized at:

  • 1μm
  • 2μm
  • 3μm
  • 5μm

These particles are much smaller than what the human eye can see. Instead, cleanrooms rely on high-quality High Efficiency Particulate Air (HEPA) filters and air quality sensors to regularly check and cleanse the air.

HEPA filters can filter the air and remove particles as small as 0.3μm with a 99.99% efficiency rating. Ultra-low particulate air filters (ULPA) remove particles as small as 0.12μm with an efficiency rating of 99.999%, which makes them ideal for more stringent cleanroom requirements.  These filters must be replaced frequently to mitigate the risk of clogs or lowered performance.

infographic hepa ulpa filters

3 States of Cleanrooms

Cleanrooms have three different states:

  1. As built. Construction is complete, but the cleanroom doesn’t have machinery, supplies, and employees yet. This state has the smallest risk of contamination.
  2. At rest. The equipment and supplies have been moved into the room, but operations haven’t yet started. Even though there isn’t activity or human movement, the cleanroom is more vulnerable to contamination in this state.
  3. Operational. In this state, the cleanroom is fully operational and staffed. This state has the highest risk of contamination.

It’s important to monitor your cleanroom for contamination at each state, but monitoring potential contamination and particulates during the operational stage is essential.

Additional Standards and Procedures

To comply with ISO standards, cleanrooms must meet strict construction and furnishing standards. At the same time, your facility may be subject to additional regulations because of your industry. Food and beverage industry facilities, for example, may not be held to as stringent standards and semiconductor manufacturers or pharmaceutical labs. Different facilities across industries may be subject to a variety of cleanroom classifications and standards, such as:

  • Good Manufacturing Practices (GMP) guidelines
  • Food and Drug Administration (FDA) air quality requirements
  • Deutsches Institut für Normung (DIN) standards
  • European standards (EN)
  • ISO 14644-1 (which establishes the nine cleanroom classes)

The choice of HEPA or ULPA filter system plays a vital role in determining the air quality of the cleanroom, as does the cleaning and maintenance routine. These additional factors should also be considered:

Materials Inside the Cleanroom

Cleanrooms need furnishings, a variety of industrial or laboratory equipment, and the goods being produced or assembled themselves. It’s important to select materials that minimize the risk of contamination and can be easily treated to continue controlling particles in the cleanroom.

Some options you may want for your cleanroom include:

  • Air showers. These spaces remove a substantial portion of particles from employees entering the cleanroom.
  • Laminar flow equipment.  The horizontal laminar flow cabinets provide a filtered airflow directed toward the user and away from the sample. This protects samples from contamination by the human operator.
  • Pass-thrus. These airlocked spaces allow materials to move in and out a cleanroom with minimal contamination transfer.
  • Tacky Mats®. Tacky mats®  feature a strong adhesive that grabs onto contaminants from shoes and foot coverings when employees walk across the surface.

Access In and Out of the Space

Every entrance and exit point should allow for a transition that minimizes contamination risks. This can include setting up entrance points with air showers and gowning areas. These precautions remove contaminating particles before employees enter the main portion of the cleanroom.

infographic cleanroom maintenance

Mistakes to Avoid When Constructing a Cleanroom

Mistakes happen, but they can drastically impede the function and quality of your cleanroom. It’s important to work with a comprehensive design and construction company that can handle every step of the process. These factors are crucial for the design and construction stages:

  • Detailed plans that articulate HVAC and filter routes
  • Comprehensive material listings
  • Adequate transition areas to minimize contamination as people or supplies enter and exit

Maintenance throughout the lifespan of your cleanroom is just as essential. Standardizing every procedure when your cleanroom is operational can help ensure consistent upkeep. Common mistakes that cleanroom managers and users make include:

  • Prioritizing speed over comprehensive care. It’s important to never skip steps during entrance, decontamination procedures, and transfer processes.
  • Allowing improper gowning and mask procedures. Human employees are one of the biggest sources of potential contamination in a cleanroom. Having adequate gowning and mask procedures is essential. It’s necessary to ensure those procedures are followed every day.
  • Not keeping detailed records. Detailed records are part of cleanroom audits and inspections. Maintaining detailed logs can also help your facility catch contamination issues or filter malfunctions before they damage research or products.

Start Building Your Cleanroom Today with Liberty Industries

Liberty Industries is a leading expert in cleanroom design and construction across multiple industries. We’ve been manufacturing high-quality cleanrooms and contamination control supplies for over 65 years.  Contact us for additional information about our comprehensive cleanroom implementation services, or request a quote to get your new cleanroom started today.



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