A Blueprint for Contamination Control
The layout of a cleanroom is a thought-provoking task that can determine its success or failure. Design elements must incorporate the facility's purpose and accommodate the scope of activities that take place within it. This section takes you on a visual tour of a hypothetical cleanroom, providing you with a snapshot view of critical areas and features that keep particulation levels low and yields high.
(A) In cleanroom environments contamination control starts at the first point of entry. In the pre-gowning area shown above workers put on basic apparel such as bouffant caps and shoe covers which allow them to move into the more regimented change room. These full gowning areas are typically one class lower than the actual cleanroom class. For example a Class 100 cleanroom utilizes a Class 1,000 change room. This means that less than 1,000 particles of contamination per cubic foot should be found in this positively pressurized environment.
(B) Change rooms often feature gowning benches and special flooring options that promote enhanced cleanliness levels. As pictured, protocols routinely require workers to don certain cleanroom garments on the outside of a bench formation and then pivot themselves to the inside of the bench of the "cleaner" side where they finish dressing and then proceed into the cleanroom on "sticky" flooring that continues to remove contaminants from the soles of their booted feet.
(C) The cleanliness class of a cleanroom determines the type of garments workers will wear inside it. The more sensitive the environment, the more clothing will be required. Gowning provides dual benefits - it protects the workers from process hazards and protects the processes from human contamination.
(D) Air locks allow cleanroom workers to move from one class to another while limiting contamination. They will typically have interlocking doors, which prevent contamination from moving between the different cleanroom classes in a facility. Air locks are most common between gowning and production areas.
(E) During work hours, cleanroom employees must remain in their cleanroom attire and follow strict operational procedures such as maintaining material flow to avoid introducing additional contamination to the environment.
(F) When exiting a cleanroom, workers throw away such disposable as hair caps, shoe covers and gloves. Larger items like bunny suits are usually used again. Procedures are determined by the class of cleanroom and the type of garment system adopted. Disposable and reusable garment systems are both viable options.
(G) Product selection is critical to maintaining a clean environment. Special items like eye washes may be required in areas dealing with dangerous chemicals. Chairs, flooring and workstations also demand serious consideration. Products must ensure safety of personnel and processes and combat such yield inhibitors as electrostatic discharge, turbulent airflows and humidity.
(H) This raised-access tile floor allows process piping and other utilities to be laid under the cleanroom. This configuration allows the manufacturer to better utilize cleanroom space and simplify routine maintenance or emergency repairs without affecting production. Raised-access flooring, however is not standard in all cleanrooms. Access flooring can be perforated which allows laminar flow typical of a Class 100 cleanroom or cleaner. For Class 1,000 cleanrooms or dirtier, access flooring can be eliminated. In these environments, static dissipative vinyl tile (SDVT) is adhered directly to the substrate.
(I) High-efficiency particulate air filtration is achieved through the use of ceiling systems like the one in this picture. HEPA filters, in conjunction with mechanical systems, remove contaminants from cleanroom environments and keep particulation temperature and humidity at specified levels.
(J) The "write" way to keep cleanrooms operating at optimal capacities is to keep workers informed and knowledgeable about protocols. In addition to formal training, written materials are usually displayed at entry and exit points, making it easy for cleanroom employees to reference them.
