IEST-RP-CC013.2, Calibration Procedures and Guidelines for Select Equipment Used in Testing Cleanroom and Other Controlled Environments, addresses aerosol photometers and Laskin nozzle aerosol generators in detail
By David W. Crosby, Air Techniques International, and Chair, IEST Working Group CC013; and Keith Flyzik, Micro-Clean, Inc., and Secretary, IEST Working Group CC013
The Institute of Environmental Sciences and Technology (IEST) has released its revised IEST-RP-CC013.2, Calibration Procedures and Guidelines for Select Equipment Used in Testing Cleanroom and Other Controlled Environments. This document provides detailed procedures for calibrating aerosol photometers and verification of Laskin nozzle1 aerosol generators, as well as “common sense” care and use guidance for general test equipment used in controlled environment testing.
Introduction
The original recommended practice (RP) was released as a tentative publication in 1986. In 2005, David W. Crosby was elected as the new chair of the WG, succeeding previous chairs Robert I. Gross and Dr. Charles Montague. With help from the WG secretary Keith Flyzik, as well as the highly motivated membership of the WG, all the necessary components of the newly revised document were completed and subsequently published in October 2006 as IEST-RP-CC013.2.
The Document
IEST-RP-CC013.2 begins with general guidelines for calibrating instruments and provides a list of instruments commonly used in cleanroom certification, including recommended calibration intervals. The document also provides guidance for transporting and packaging instruments and also includes a procedure for anemometers. It addresses both Laskin nozzle and thermal aerosol generators, as well as both linear and logarithmic photometers. Generic calibration procedures are also provided along with a sketch of a 100 μg/L aerosol source, which is important in calibrating a photometer’s internal aerosol reference feature. The appendix lists most other instruments currently used in cleanroom certification and, where available, relevant instrument calibration references to appropriate national standards (ASTM, ISO, etc.).
Calibration guidance for the aerosol photometer consumes a majority of the newly published document. In a world of lasers, solid-state microprocessors, and emerging technologies, it is still amazing that the basic principles of operation of the aerosol photometer and Laskin nozzle aerosol generator have not changed significantly over the decades. Although many current production aerosol photometers now have microprocessors, digital displays and monitoring circuitry, most still rely on a photomultiplier tube-a vacuum electron tube-as the light detector.
Although the document provides the basic calibration procedures used by a variety of photometer manufacturers and calibration groups, it does not contain “how-to” guidance for specific model adjustments, alignments or diagnosing problems. That information is available by consulting individual manufacturers, attending specialized training and, in cases of problem diagnosis, from years of experience.
While IEST-RP-CC013.2 is important to the cleanroom and HEPA-filter testing industries, it is crucial to those involved with testing and certification of Class II biological safety cabinets (BSCs). The aerosol photometer is the only approved instrument listed in NSF/ANSI 49-20042 for performing the HEPA Filter Leak Test. This is mainly due to the fact that most photometers are equipped with an internal reference function to simulate a known aerosol challenge. This allows the certifier or tester to leak-test the HEPA filter without taking an upstream concentration, thereby preventing exposure of personnel, equipment and environment to potential contaminants trapped in the upstream plenum of the filter.
Verification of the operation of the Laskin nozzle generator becomes increasingly important when testing HEPA-filtered devices where an upstream challenge is either impractical or impossible due to safety concerns. The new RP provides detailed guidance on this procedure.
Those individuals involved in the NSF Biosafety Cabinet Field Certifier Accreditation Program should become familiar with IEST-RP-CC013.2 since it has historically been a study reference for the written examination and will have applications in the practical examination.
Finally, there is a “common sense” appendix that discusses proper instrument care. Much of this experience and many of these practices are a collection of simple guides obtained from decades of test equipment use and repair knowledge. The intention of the WG was to present these guides or care rules to prevent lessons from being learned “the hard way.”
The future
The WG plans to continue to create informative calibration procedures for equipment lacking industry-acknowledged calibration methods. However, it has no wish to compete against other organizations with previously established and available calibration procedures. In such cases, published calibration procedures would be referenced in an informative appendix for each type of equipment used in testing cleanrooms and controlled environments. The intention is that the RP become a single-source reference document for calibration resources. Although the listings in the current version are by no means complete, the document makes an effort to provide current and available information to those needing it most (i.e., calibration organizations, regulatory authorities, quality assurance groups, and test equipment end users). With the December 2005 publication of ISO Standard 14644-33, WG-CC013 has its work cut out for itself: to investigate calibration methods for equipment referenced in the document, which will allow for global application of IEST-RP-CC013.2.
The RP has also become a “nursery” for new test methodology. Just recently, the IEST established WG-CC042, Liquid-borne Particle Counting, to address issues involving liquid-borne particle counters (LPCs). The idea had its origins during WG discussions and deliberations. Other new WGs may follow depending on interest, participation of qualified and experienced volunteers, and the needs of the contamination control industry.
Although we are beyond merely “scratching the surface” on calibration procedures for cleanroom and other controlled environment testing equipment, we are nowhere close to being finished with the job. We ask for comments or suggestions on this latest version of the RP but, most of all, we ask for your active participation in moving this document to the next level. We invite anyone with a real interest in developing calibration procedures to attend future IEST working group meetings.
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David W. Crosby has been active in the air filtration and respirator industry for more than 40 years. He started with Air Techniques International in 1962 and currently serves as vice president and manager of the ATI Test Laboratory. He has managed and been involved with design, engineering, quality control and government contract administration. He holds degrees in electronics, heating/air conditioning/refrigeration and business management. Crosby is an active member of the IEST, the International Society of Nuclear Air Treatment Technologies, the American Society of Mechanical Engineers and the Controlled Environment Testing Association. He currently serves on IEST working groups 001, 002, 006, 007, 019, 021, 034, and chairs 013.
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Keith Flyzik is technical liaison and training manager for Micro-Clean, Inc. where he is responsible for all training programs for technical personnel and customers as well as keeping personnel current on regulatory agency issues and guidelines, industry recommended practices and equipment manufacturer specifications. In his 16 years with Micro-Clean, he has also held positions of certification technician, calibration technician, technical services manager and quality assurance manager. As an active member of IEST, Flyzik serves as the secretary for WG-CC13 and holds voting-member status on numerous other contamination control work groups. He is also a member of the Controlled Environment Testing Association, serving on the Cleanroom, Isolator Guide and Isolator Testing committees.
About IEST
Founded in 1953, 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 an ANSI-accredited standards-developing organization; Secretariat of ISO/TC 209 Cleanrooms and associated controlled environments; Administrator of the ANSI-accredited US TAGs to ISO/TC 209 and ISO/TC 142 Cleaning equipment for air and other gases; and a founding member of the ANSI-accredited US TAG to ISO/TC 229 Nanotechnologies.
References
- Echols, W. H. and J. A. Young, “Studies of Portable Air Operated Aerosol Generators,” U.S. Naval Research Laboratory (NRL) Report 5929, Washington, DC, 1963.
- NSF/ANSI Standard 49: Class II (Laminar Flow) Biosafety Cabinetry, NSF International, Ann Arbor, MI, www.nsf.org.
- Cleanrooms and associated controlled environments-Test methods, International Organization for Standardization, Geneva, Switzerland.