IEST-RP-CC023.2: Microorganisms in Cleanrooms

BY Mike Rataj, National Quality Assurance Manager, ARAMARK Cleanroom Services

The cleanroom has developed as an essential part of the process of manufacturing medical devices, electronics and pharmaceuticals. These ultraclean environments make the most sophisticated electronics or medications possible while ensuring product quality and consumer safety. Cleanrooms are usually designed to control particulate contamination, but sooner or later when operating a cleanroom, one will have to address the presence of microorganisms. Microorganisms pose a unique threat to cleanroom operations because they produce both particulate contamination and unwanted metabolic products that can also act as contaminants. The Institute of Environmental Sciences and Technology (IEST) has been a leader in developing recommended practices intended to aid in the implementation and operation of the cleanroom for all types of applications. The newly revised Recommended Practice IEST-RP-CC023.2: Microorganisms in Cleanrooms provides a comprehensive assessment of the process and tools used to achieve the highest levels of microbial control.

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The Recommended Practice (RP) is intended to assist anyone responsible for cleanroom operations with assessment and correction of any type of microbial problem that may occur in the cleanroom. The committee sought the collective experience of experts from all areas of the cleanroom industry from aseptic processing to aerospace to microelectronics. The RP provides a ready resource that can be used to design a control program or to address a short-term problem in the cleanroom. Table 1 is a general summary of the source and types of contamination that impact cleanroom operations. Each of the control strategies discussed requires a comprehensive monitoring program to ensure effectiveness.

Strategic planning

The RP discusses the need to begin any microbial control program with a plan that is based upon the risk posed to the product or process. The planning process must take into consideration the design elements of the cleanroom, the potential source of contamination, and the control methods used to address the sources of contamination, as well as levels of contamination expected. A good plan will help achieve the level of control required and will provide a sound baseline from which any investigation into a problem can start.

Cleanroom garments

Cleanroom garments are used to contain or isolate the microbial contamination that is generated by the operator during normal operations. In the most critical applications, which involve the aseptic processing of products, all of the operator-associated contamination must be eliminated from the environment. The RP provides a typical gowning protocol and discusses the types of gowning required by various levels of cleanroom. If there is a need for sterile garments, the document describes the procedure used to validate and support the sterilization of garments via ANSI/AAMI/ISO 11137-1994 Sterilization of health care products-Requirements for validation and routine control-Radiation sterilization. Irradiation is the preferred method for the sterilization of garments due to its effectiveness and potential for immediate release after processing.

Environmental monitoring

Environmental monitoring is used to evaluate the performance of the cleanroom. All certified cleanrooms are tested for airborne particulate at some frequency that is based upon the class of the cleanroom. This routine particle monitoring is useful in judging the overall cleanliness of the cleanroom but is not an accurate guide to the level of microbial contamination in the room. Bacteria and fungi are detected as particles but there is no way to determine if they are viable through this testing. The RP provides a framework for assessing and correcting any microbial issues in the cleanroom. These areas are described in detail.

Surface monitoring

Surfaces are typically monitored for microbial contamination by collecting the residual contamination and culturing it. The document outlines a process for implementing a monitoring program and provides the information required to collect and interpret the data that is collected.

Airborne contamination

After the operator, the infiltration of the ambient environment is the largest source of microbial contamination. Generally contamination is transported most efficiently throughout the room if it is airborne. The various methods and devices for collecting this type of contamination are discussed and a comparison of the relative merits of the methods is made. This will help determine how much of each type of testing is required. A comprehensive discussion of the types of powered sampling devices is also presented.

Enumeration and interpretation

All microbial environmental-monitoring methods require some type of media and incubation to enumerate the organisms collected. The media and culture conditions must be tailored to the target organism. The RP provides guidance on the choice of media and media additive that should be used to maximize the effectiveness of the program. The proper media and additive can ensure against an error in the assessment of the quality of the room. The implementation of Alert and Actions limits is discussed as a valuable aid in developing a method for responding to the information collected during monitoring. The need to trend results and track subtle changes and the use of statistical methods to help with the management of the control program are discussed at some length.

Cleaning and disinfection

The choice of cleaning agents and methods can be critical to the success of any microbial control program. Incorrect cleaning methods or materials can result in enhancing contamination instead of controlling it. The relative characteristics of cleaning/disinfection agents are discussed. The RP provides guidance on the use and misuse of these agents and methods.

IEST-RP-CC023.2 represents the current knowledge of a wide range of cleanroom-industry microbiologists who work in a number of applications ranging from laboratory testing to aseptic processing. The committee has produced a document that will be a valuable tool for any cleanroom operator or manager who is looking to implement an effective microbial control program for the cleanroom. The document provides the detail necessary to establish a meaningful monitoring program, which is the only way to measure the effectiveness of all the control strategies that have been used. Although it is inevitable that microorganisms will get into a cleanroom, one can be assured that the control methods and processes discussed will minimize the potential for damage in the cleanroom.

Mike Rataj is the national quality assurance manager for ARAMARK Cleanroom Services, Inc. He has over nine years of experience in the contamination-control industry and performs consulting and validation testing for various pharmaceutical and medical device companies. Prior to coming to ARAMARK, Mr. Rataj worked in the microbiology field for eleven years in academics and in the industrial and pharmaceutical industries. He has a BS and an MS in biology from the University of Illinois in Urbana, Illinois. His activities have included both R&D and production of pharmaceutical and animal health products. He is a member of IEST.

About IEST

IEST is an international technical society of engineers, scientists, and educators that serves its members and the industries they represent (simulating, testing, controlling, and teaching the environments of earth and space) through education and the development of recommended practices and standards. IEST is the Secretariat for ISO Technical Committee 209, Cleanrooms and associated controlled environments, charged with writing a family of international cleanroom standards. IEST is also an ANSI-accredited standards-development organization. For more information, contact IEST at [email protected] or visit the IEST Web site at


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