Tuesday, April 12, 2011

The Causes of Cleanroom Contamination

By Graham O'Keeffe

Of the many potential sources of contamination in cleanrooms and other clean manufacturing environments, none is more persistent, pervasive or pernicious than the human beings who occupy them. There are many possible sources of contamination of the cleanroom environment. Equipment, structures, and surfaces can generate particles through friction, heat, exhaust, outgassing, and static electricity. Incoming production components may introduce contaminants. Still, it is the people working in the cleanroom that generate the most particles. Of the many elements of cleanroom operations and processes, humans are the easiest to control, yet contribute the most contamination.

While non-particulate contamination (non-volatile residue or airborne molecular contamination, for example) is a concern in many applications, the fundamental aspect of the cleanroom environment is an effective cleanroom management program that keeps the environment free of airborne particles. As cleanroom operators are working, they generate millions of particles with every movement. Schlieren thermal images show particles emitted from the human body. Particles migrate up through the cleanroom apparel toward the head and fall down the legs during cleanroom activities.

Bacteria, molds, and yeast are viable organisms which are chemically active and can reproduce fast. Based on the nature of chemicals released during their growth and replication, these byproducts can cause a variety of contamination in the cleanroom. Humans are no different when it comes to generating elemental chemicals that can cause contamination: Spittle: potassium, chloride, phosphorus, magnesium, and sodium. Dandruff: calcium, chloride, carbon, and nitrogen. Perspiration: sodium, potassium, chloride, sulphur, aluminium, carbon, and nitrogen. Fingerprints: sodium, potassium, chloride, and phosphorus

Cleanrooms are planned and manufactured using strict protocol and methods. Many cosmetics contain sodium, magnesium, silicon, calcium, potassium or iron. These chemicals can create damaging particles. Cleanroom managers may ban or restrict cosmetics in the cleanroom. This is usually dependent upon the threat to the product being made in the cleanroom. "Just as humans are the greatest potential contamination risk, they are also the greatest resource for contamination control." A full, systematic, and comprehensive training program detailing all aspects of cleanroom management will enable the cleanroom operators to control the degree of contamination during the production process.

Other behavioral standards include, but are not limited to the following: Smoking is not allowed inside the manufacturing facility including all cleanroom areas. Smokers release tar particles for at least one-half hour after smoking one cigarette. Personal items such as jewelry or keys, cosmetics, tobacco or matches, food and beverages in any form are strictly prohibited in the cleanroom as well as all the items not related to the cleaning/manufacturing processes. Hair may not be combed in the cleanroom gowning area. Only cleanroom approved ballpoint pens are permitted inside the cleanroom for recording data on cleanroom compatible paper and clipboards. Avoid mannerisms such as scratching or hand-rubbing while working in the cleaning rooms. Cleanroom personnel may not access the inside of the cleanroom uniform. The use of facial tissues is prohibited in the cleanroom. Use a non linting tissue if absolutely needed in the gowning area and dispose appropriately. All doors must be closed when not used in either entering or exiting. Emergency doors may be alarmed with a visual and audible alarm to enforce compliance. No touch techniques. It is considered best if you can manipulate materials without having to use your hands. Though wearing gloves does reduce potential contamination the risk still exists. Though clean room surfaces and clothing are freer of bacterial and fibers that cause contamination, the less you can touch any of the clean room surfaces with gloves or your body is recommended.

We hope that this article has provided you with insights of why and how people are considered to be the number one supplier of cleanrooms contamination.

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1 comment:

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