Changes in Clean Room ISO Standards

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Last December, international experts unveiled drafts of updated international ISO cleanroom standards that could have consequences for clean room design, implementation, and manufacturer practices in the future. The revised standards have introduced an improved statistic-based plan for room cleanliness that focuses on particle concentrations in various areas of the room to gain a more accurate reading of overall room concentration.

The US FDA has not made any official comment on the revised standards, but the Division of Manufacturing and Product Quality within FDA’s Center for Drug Evaluation and Research has commented that they are supportive of efforts to improve standards and encourage them to be followed internationally.

Since the new standards mark such a noticeable departure from previous standards, more opinions will undoubtedly arise as to the effectiveness of the new standards. The standards feature a procedure of random sampling that may force manufacturers like pharmaceutical producers to update their protocols for sampling and testing a room’s cleanliness.

Some manufacturers may object to these new procedures on various grounds, but the experts behind the updated standards have argued that the statistics have shown that the new approach is more beneficial and have published a paper to prove their point. Time will tell how the overall set of guidelines is received by the various industries to be affected.


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What is a Cleanroom Anyway?

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A clean room is a building that is constructed to provide for a clean environment for various fields of research such as biological or chemical research, and also for the manufacturing of sensitive components. These purposes often involve environmentally sensitive processes that require an uncontaminated environment. These processes are conducted with procedures that are intended to prevent the contamination of the environment with foreign matter like airborne particles and bacteria; these procedures range from a strict employee dress code, rigorous washing, environmentally isolated lockers and chambers, air showers, and thorough cleaning techniques. The design of the clean room itself incorporates HEPA and ULPA filters to facilitate an air flow through the facility that keeps out contaminants, generally with a positive pressure flow to push contaminants out, or a negative pressure system that keeps everything in, depending on the design objectives.

An example of scientific research that would require a clean room would be when scientists grow cultures that would be ruined if bacteria were to contaminate them. In manufacturing, there are many components that require a clean, uncontaminated environment to be made in, such as microprocessors which could be inhibited with the slightest trace of a foreign particle such as dust or dirt. Generally, employees who work in clean rooms are required to follow specific guidelines for keeping out external contaminants. They will often wear protective clothing with hood coverings, gloves, and masks. They will also pass through air showers to get rid of any particles from the outside before stepping into the clean room environment.

Clean rooms come in several forms, depending on the requirements of the facility. Some clean rooms are hard-walled facilities that are permanent, and then some are flexible soft-walled facilities which can be easily transported, such as for medical emergencies. Some facilities are modular in construction, and can be broken down and moved or kept permanent, depending on preferences.

Clean rooms follow a grading scale that measures the amount of allowable contaminant particles in the air. The ISO system starts at ISO 1, which allows 10 or fewer particles per every 0.5 micrometer cubic area. The allowable particles increase by a factor of 10 with every increase in the ISO rank. Another grading scale that is used is the US federal standard which is numbered 1, 10, 100, 10,000, and so on. Class 1 rooms have 1 particle for every 0.5 micrometer of cubic space, and so on, the Class numbers resembling the maximum amount of particles allowed in 0.5 cubic micrometers.

As for the filtration systems, clean rooms often use HEPA filters and ULPA filters. These filters can remove up to 99.9 percent of the particulates in the air using various air flow systems. There are laminar air flow filters which employ unidirectional airflows; this means that air flows in a straight downward motion, cleaning any particulates. There is also a non-unidirectional airflow type which creates turbulent air conditions which can separate air particles from the air. Some clean rooms employ a positive pressure to keep particles out, and then some employ negative pressure to keep contaminants in. It all depends on what needs to be done in the workspace.

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Air Flow Principles for Cleanrooms

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Cleanrooms are generally buildings that are designed for conducting sensitive scientific research or handling and manufacturing products that require uncontaminated environments. Usually cleanrooms use a variety of mechanisms, design features, and safe guards to prevent foreign particles, bacteria, and other similar contaminants from entering the workspace. Special employee uniforms and washing habits, separate sealed chamber and locker anterooms, and rigorous cleaning techniques with special materials and solvents are among these measures. In addition to those measures, one of the major factors keeping a cleanroom free from outside contamination is the integrated air filter system. Clean rooms can employ varying types of filters, such as HEPA and ULPA filters; these filters generally employ airflow principles such as laminar and turbulent airflow principles.

Cleanroom Basics

Clean rooms are used for sensitive scientific research that requires uncontaminated environments that are free from outside particles and bacteria. For example, when scientists grow cultures, it is important to isolate the task from foreign bacteria so that results will not be compromised. When it comes to manufacturing various kinds of products like microprocessors, the workspace needs to be a particle-free environment, because even a bit of dust contaminating the small chips of a microprocessor can compromise the product.

Cleanrooms come in several forms. These forms are usually divided into hard walled and soft walled. A hard wall clean room is a permanent structure or part of a larger permanent structure and generally doesn’t go anywhere. A soft wall cleanroom can be rearranged, expanded, or even transported depending on task requirements. Soft wall clean rooms are usually built within a larger, permanent structure. Soft wall cleanrooms (which are usually modular in design) are generally useful for medical emergencies or when requiring smaller scale, shorter timeframe manufacturing projects due to their flexible nature.

Cleanrooms are classified according to the amount of particles present in the air. There are two different standards used for these classifications depending on their use: the ISO classification and United States classifications specified by federal standards. ISO grades are numbers that correspond to factors of ten, starting from 1. A cleanroom graded ISO 1 contains ten or fewer particles per 0.1 micrometer cubed area; a cleanroom graded ISO 2 contains 100 or fewer particles per 0.1 micrometer cubed area; and so on. US federal standards are numbered 10, 100, 1000, etc., with each class specifying how many particles are in a 0.5 micrometer cubic area. Class 1 cleanrooms have one or fewer particles per 0.5 micrometer cubed area. Class 10 cleanrooms have 10 or fewer particles per 0.5 micrometer cubed area.

In order to limit the amount of particles they track into the cleanroom or particles they shed while working in the environment, workers are usually required to follow dress and cleanliness guidelines. Workers change into specially designed outfits, often with hood coverings, gloves, and breathing masks to keep the head covered. Workers also enter through an air shower to eliminate any lingering particles and then pass items into the cleanroom through a small antechamber that prevents outside air from entering the clean environment. Shoe scrubbers can also be used to prevent tracking in more particles.

Cleanroom Air Filtration

Clean rooms employ unique cleanroom-specific air filtration to limit the particles in the environment air. Typically, this is through the use of either a highly efficient particulate air (HEPA) or ultra low particulate air (ULPA) filter. These filters can remove roughly 99.9 percent of all micro particles in the air by applying either laminar air flow techniques or turbulent air flow techniques to the environment air.

Laminar air flow consists of air that flows in a straight path. Unidirectional air flow is maintained in clean rooms through the use of specialized laminar air flow hoods that direct air jets downward in a straight path, as well as cleanroom architecture that ensures turbulence is lessened, such as smooth surfaces and streamlined design. Laminar air flow utilizes HEPA filters to filter the air in the environment. Laminar filters are often composed of stainless steel or other non-shed materials to ensure the amount of particles that enter the facility remains low. Cleanrooms employing laminar air flow are generally known as Unidirectional Airflow Cleanrooms.

Non-unidirectional airflow clean rooms utilize turbulent airflow systems to clean air of particulates and maintain a clean environment. The entire enclosure is designed to use laminar flow and random, non-specific velocity filters to keep the air particle-free. Turbulent airflow can cause particle movement that can be difficult to separate from the rest of the air, but non-unidirectional airflow systems count on this random movement to move particles from the air through the filter.

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