Cleanroom Introduction


The need for a clean environment in hospitals is rooted in the control of infections. Microbiologists and surgeons for the past 100 years have known that bacteria cause wound infections. It follows that the elimination of bacteria from the hospital and, in particular, the operating room, prevents infection. This is the scientific basis for the first clean rooms. The control of infection was approached using antiseptic techniques to clean instruments, wounds and surgeons' hands. To prevent airborne infection the same antiseptic solution was sprayed into the air. Later aseptic techniques such as sterilization of wound dressings and instruments and the use of surgical gloves, masks and gowns were adopted to further reduce infection. Although antiseptic and aseptic techniques helped control infection, the principal omission was positive ventilation by filtered air.

It was found that proper ventilation substantially reduced airborne infection of people. But, it is only towards the end of the Second World War that ventilation in hospitals was adopted for contamination control. The development of the first clean rooms for industrial manufacturing started during the second World War in the United States and England in an attempt to improve the quality and reliability of instrumentation used in guns, tanks and aircraft. It was realized that the cleanliness of the production environment had to be improved or such items would malfunction. It therefore followed that airborne dispersion of large quantities of particles by machines and people had to be removed by large quantities of filtered air.

What is Cleanroom


Airborne particles occur in nature as pollen, bacteria, miscellaneous living and dead organisms, windblown dust, and sea spray. Industry generates particles from combustion processes, chemical vapors, and friction in manufacturing equipment. People in the workspace generate particles in the form of skin flakes, lint, cosmetics, and respiratory emissions. Today, many manufacturing processes require that spaces be designed to control particulate and microbial contamination while maintaining reasonable installation and operating costs. Federal Standard 209E defines a clean room as a room in which the concentration of airborne particles is controlled to specified limits. British Standard 5295 defines a clean room as a room with control of particulate contamination, constructed and used in such a way as to minimize the introduction, generation and retention of particles inside the room and in which the temperature, humidity, airflow patterns, air motion and pressure are controlled. The industry differentiates between the cleanliness of rooms by referring to class numbers. The method most easily understood and universally applied is the one suggested by the Federal Standard 209E in which the number of particles equal to or greater than 0.5 microns measured in a cubic foot of air designates the class number. For example, a class 100,000 clean room limits the concentration of airborne particles equal to or greater than 0.5 microns to 1 00,000 particles in a cubic foot of air.

Clean rooms have evolved into two major types which are differentiated by their method of ventilation - turbulent airflow and laminar airflow clean rooms. The general method of ventilation used in turbulent airflow clean rooms is similar to that found in buildings such as offices, schools, malls, manufacturing plants, auditoriums, shops, etc. The air is supplied by an air conditioning system through diffusers in the ceiling. However, a clean room differs from an ordinary ventilated room in three ways. These are increased air supply, the use of high efficiency filters and room pressurization. The increased air supply is an important aspect of particle control. A typical turbulent airflow clean room would have at least 10 air changes per hour and likely have between 20 and 60. This additional air supply is mainly provided to dilute to an acceptable concentration the contamination produced in the room. High efficiency filters are used to filter the supply air into a clean room to ensure the removal of small particles. The high efficiency filters used in clean rooms are installed at the point of air discharge into the room. Room pressurization is mainly provided to ensure that untreated air does not pass from dirtier adjacent areas into the clean room. The clean room is positively pressurized with respect to these dirtier areas. This is done by extracting less air from the room than is supplied to it.

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Class Limits


Testing


USP797


Definitions


Annual Maintenance Contract.


1) AHUs, Cleanrooms, Laminar Flow work stations.
2) Largest inventory of air filters [20, 10, 5, 3 micron] pre filters and hepa filters.
3) Room differential pressure management.
4) Periodical testing & Validation of cleanrooms.