Production facilities and laboratories need to observe the highest standards of cleanliness. A cleanroom is an enclosed area of a facility designed to maintain extremely low levels of contaminants such as vaporized particles, airborne organisms, and dust. Cleanrooms are used for scientific research and the production of precision electronics, pharmaceuticals, and other highly sensitive products.
Some of the industries where cleanrooms are commonly used include:
Cleanrooms have specific ISO class code descriptions that provide secure environments through controlled air filtration and protective guidelines. That reduces the possibility of large particulates interfering with critical process manufacturing or the possibility of product contamination. Cleanroom classifications also require facilities to maintain positive pressure as long as the cleanroom is operational. It prevents the flow of contaminated air back into the environment by continuously flowing filtered air to less-clean spaces.
Basic Cleanroom Requirements
A clean environment is a requirement for most industries. Cleanrooms are among a production cycle's most important components, as they enable processors and manufacturers to work in safe environments and put out high-quality products but different industries have different criteria for cleanliness. Therefore, cleanrooms also have varying levels of tolerance for particles.
The classification of these tolerances is done in line with the International Standards Organization (ISO) guidelines. However, there are basic requirements that every cleanroom should meet. They include:
The level of cleanliness in cleanrooms is quantified by the number of particles in every cubic meter at a predetermined molecule measure. Class 1 facilities have the lowest level of contaminants while Class 9 facilities have the highest. The typical urban outdoor air has 35,000,000 particles per cubic meter at a 0.5-micrometer size range. This is the same as an ISO 9 cleanroom. An ISO 1 cleanroom contains 12 particles per cubic meter at a size range of 0.3 micrometers. At 0.5 micrometers, an ISO 1 cleanroom doesn't have any particles.
The classification of cleanrooms is usually done according to the size and number of particles permitted per volume of air. Cleanrooms should not exceed a particulate count as specified in its air cleanliness class. Until 2001, the Federal Standard 209E was used before it was replaced with the ISO 14644-1. The federal standards used cubic feet in measuring the size while the ISO standards rely on cubic meters. As a result, Class 1 was the cleanest according to federal standards but corresponded only to ISO 3 under the ISO 14644-1 standards.
See the table below for a summary of the classification of cleanrooms:
Cleanrooms are regularly tested and inspected to guarantee their effectiveness. The higher a cleanroom's classification, the more inspections it undergoes but the inspections are typically connected to compliance testing which is done once or twice per year.
The testing and characterizing of cleanroom performance are done at three different levels of conditions. They include:
ISO 7 Cleanroom Standards
Industries such as pharmaceutical labs, specialist manufacturing facilities, and testing booths generally use ISO 7 cleanrooms. They are designed to prevent the contamination of processes going on inside the room.
The minimum standards for ISO 7 cleanrooms include:
The ceiling coverage of an ISO 7 cleanroom is between 15 and 25%. ISO 7 cleanrooms are mostly used to prepare solutions that need filtering, production processing, and specialist component handling.
ISO Class 8 Cleanroom Requirements
ISO 8 cleanrooms are mostly used for aerospace product development, cosmetic lines, bottling lines, pharmaceutical compounding, electronics production, and production of medical devices.
Unlike ISO 7 cleanrooms, ISO 8 cleanrooms don't require testing for certain particle sizes as they either have very high or low concentration levels for testing. However, the particle sizes can't be zero. Particles that are smaller than 0.5 µm aren't usually considered while concentration levels for particles that are less than or equal to 0.5 µm should be less than 3,520,000.
The air change rate for a class 8 cleanroom should be 5 to 48 every hour with a 5-15% ceiling coverage. An ISO 8 cleanroom is also required to be fitted with HEPA filters.
Air Changes Per Hour For Cleanrooms
For the other classes of cleanrooms, the rate of an air change per hour is as follows:
Cleanroom Pressure Differential Calculation
Air change rates help facilities determine the design and performance criteria for a cleanroom's air system. The total air change rate, flow pattern, and efficiency of the exchange have an impact on the cost and performance of a cleanroom.
Differential pressure refers to pressure deviation between two points in different pressure systems. Different cleanroom classes require a specific number of air changes per hour and differential pressure is key to maintaining a particular classification. It ensures that the correct operation and efficiency of a cleanroom are met.
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