FS209E – Class 1 – 100,00
Before universal clean room classifications and standards were taken over by the International Standards Organization (ISO), the U.S. General Service Administration’s standard (FS209E) were lived and died by for contamination control. The FS209E had 6 classes. The “cleanest” clean room being referred to as a class 1 and the “dirtiest” clean room referred to as a class 100,000. However, the FS209E was cancelled by the General Services Administration of the US Dept. of Commerce in 2001. The forecast internationally for this standard is to be phased out in the next 5-10 years.
ISO Classifications 14644
While class 100 and 10,000 are imprinted on many brains, ISO 14644-1 is the new standard for clean room classification. ISO 14644-1 classification system adds 2 cleaner standards and one dirtier standard to the previously used FS209E clean room standards. There are 9 ISO classifications, ISO 1, ISO 2, ISO 3, ISO 4, ISO 5, ISO 6, ISO 7, ISO 8, and ISO 9. ISO 1 is the cleanest and ISO 9 is considered the dirtiest. The foundation of cleanroom standards is the micrometer or micron, and each ISO class has a threshold of allowable particles to determine the ISO classification for the clean space. See ISO classification chart below.
Particle concentrations having cumulative counts of particle sizes range from 0.1 µm to 5 µm are considered for classification purposes. Anything smaller than 0.1 µm are ultrafine particles and addressed by a different standard using nano-scale particles.
What’s the size of a micron?
To put it in perspective the average human hair is 50-70 microns while fine beach sand is 90 microns.
Laminar and Turbulent Air Flow
ISO 5 and cleaner facilities (ISO 1, 2, 3, and 4) utilize unidirectional or laminar airflow. This means that filtered air is distributed uniformly in a single direction at a consistent velocity through parallel streams, typically vertically. The air is usually recirculated from the base of the walls to the filtering system.
Cleanrooms classified as ISO 6 and dirtier (ISO 7 and 8) typically use a non-unidirectional or turbulent airflow. In contrast to laminar airflow, the air in these cleanrooms is not controlled for direction and speed. While turbulent airflow has its advantages, laminar airflow offers a more uniform environment and reduces the risk of contaminants gathering in pockets of stagnant air.
ISO Class Specifications
The ISO class required in a cleanroom can vary depending on the task at hand, with some tasks requiring minimal filtration and others requiring extremely advanced filtration capable of removing even the smallest particles. Cleanrooms also regulate several other properties including temperature, humidity, airflow, filtration, and pressure.
ISO 1 classified cleanrooms are the most stringent ISO classification, requiring less than or equal to 2 particles larger than 0.2 microns and no particles larger than 0.3 microns per cubic meter. To achieve this level of cleanliness, they typically have a high air exchange rate of 360-600 air changes per hour and use ULPA filtration. Other common features include laminar air flow with 100% ULPA filtration covering 80% - 100% of the ceiling. The airflow system is designed to remove microscopic particles from the body, typically through a grated floor access.
ISO 2 classified cleanrooms must have less than 100 particles equal to or smaller than 0.1 microns and no particles larger than 1.0 microns per cubic meter. They typically have a high air exchange rate of 360-600 per hour and use ULPA filters. Like ISO 1, common characteristics include 80% to 100% ULPA-filtered ceiling coverage, as well as laminar air flow. ISO 2 cleanrooms often incorporate grated floors in the design to remove particles. It is the second highest level of cleanliness.
ISO 3 classification for cleanrooms, there must be no more than 102 particles larger than 0.3 microns and a maximum of 8 particles larger than 1.0 microns per cubic meter. These cleanrooms usually have a high air exchange rate of 360-540 per hour and use ULPA filters. Other common characteristics include ULPA-filtered ceiling coverage of 60% to 100% and grated floors to remove particles. It is the third highest level of cleanliness.
ISO 4 classification for cleanrooms stipulates that cleanrooms must have no more than 1020 particles larger than 0.3 microns and a maximum of 352 particles larger than 0.5 microns per cubic meter. These cleanrooms typically have a moderate air exchange rate of 300-540 per hour and use ULPA filters. Other common features include ULPA-filtered ceiling coverage of 50% to 90% and grated floors. It is the fourth highest level of cleanliness.
ISO 5 classified cleanrooms are engineered to maintain a high level of air purity. These rooms are equipped with ULPA or HEPA filters that ensure a maximum of 3,520 particles larger than 0.5 microns per cubic meter. To achieve this level of cleanliness, ISO 5 cleanrooms typically use laminar airflow and have a recommended ceiling coverage of 35-70% filtration and 240-480 air changes per hour. This combination of filtration and airflow helps to keep particulate contamination at a minimum.
ISO 6 classified cleanrooms are engineered to have low levels of particulate contamination. These rooms are required to have no more than 35,200 particles larger than 0.5 microns per cubic meter and must have 100-240 air changes per hour filtered through HEPA filters. To achieve this level of cleanliness, ISO 6 cleanrooms should have HEPA filter ceiling coverage of 25-40%. These cleanrooms can be designed with either laminar or turbulent airflow.
ISO 7 classified cleanrooms must maintain a certain level of air purity, with no more than 352,000 particles larger than 0.5 microns per cubic meter. To achieve this level of cleanliness, these rooms must have 20-90 air changes per hour filtered through HEPA filters. To ensure optimal performance, ISO 7 cleanrooms should have HEPA filter ceiling coverage of 15-20%.
ISO 8 classified cleanrooms must have a maximum particle count of 3,520,000 particles larger than 0.5 microns per cubic meter and a minimum of 5-30 air changes per hour, which must be filtered through HEPA filters. The recommended ceiling coverage is between 5% to 15%.
ISO 9 cleanrooms are classified as normal room air, with a maximum particle count of 35,200,000 or fewer particles measuring 0.5 microns, 8,320,000 or fewer particles measuring 1 micron, and 293,000 or fewer particles measuring 5 microns.
ISO Classification Recommended Air Changes
When determining the appropriate velocity and air changes for a clean room, it is important to carefully consider factors such as the number of personnel, the effectiveness of garbing protocols, and the cleanliness of process equipment. By considering these factors, the required air change figure can be established. Once this figure is determined, the number of filter units needed can be calculated.
Also, as the Cleanroom industry has evolved and learned more over time, higher air change rates does not always mean “better” in the way of performance testing when it comes to particulate counts in meeting the ISO classifications. There are more efficient ways to design a cleanroom, such as the enclosure design and proper air distribution for example, protocols, etc. that allow us to achieve proven results vs. the older air change recommendations of the past. This result can save up front cost on lesser equipment sizes, and in operating energy costs in conjunction of design sizes.
Different classes of cleanrooms have recommended air change rates that vary because of the occupancy states. As-built and at-rest facilities typically require a lower air change rate than operational cleanrooms where people and equipment are active. The air change rate for non-operational cleanrooms will be on the lower end, while operational cleanrooms will have a higher air change rate.
ISO Clean Room Occupancy States
As-built – The clean room is complete and operational with nothing inside (equipment, materials, or personnel)
At-rest – The clean room is complete and operational with equipment installed but with no personnel present.
Operational – The clean room is complete and operational with equipment installed and personnel present.
The Importance of Positive Pressure in A Clean Room
Clean rooms are created to maintain a positive pressure to prevent contaminated air from entering and less clean air from flowing into the clean areas. The goal is to maintain a constant flow of filtered air from the cleanest to the least clean spaces.
In a multi-chambered cleanroom, the room with the highest level of cleanliness is maintained at the highest pressure. The pressure levels are set in a way that the cleanest air flows into spaces with lower levels of cleanliness. Therefore, multiple pressure levels may need to be maintained to ensure optimal air flow.
It is recommended to have a pressure differential of between .03 and .05 inches of water gauge between spaces. To maintain a consistent air pressure differential, control systems must be implemented. This is particularly important when doors are opened, or other events occur that may affect pressure differentials in the clean room.
Energy Efficient Clean Rooms
When creating a clean room, enclosure, or laboratory, we focus on maximizing energy efficiency in all aspects of the design. This includes utilizing the most advanced thermal envelope materials and designing the most efficient HVAC systems. One way we achieve this is by recirculating a high percentage of conditioned air, which helps reduce energy consumption. The combination of thoughtful design, strategic material selection and proper installation are crucial factors that contribute to the overall performance of the build.
Clean Rooms & ISO Classifications
What is a Clean Room?
Before understanding ISO classifications it’s imperative to know “what is a clean room”. A clean room is an environmentally controlled space where the ISO classification of airborne particle concentration is specified. A well-designed clean room is constructed to control the introduction and generation of particles inside the room using filters and air pressure to maintain the specified ISO clean room class. Prior to designing and constructing an ISO clean room, it is important to know what size particle will affect your product or procedure. Each process is unique and requires proper planning and execution.
