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PortAll and Cleanroom
Classification Standards 1st Revision - January 7, 1999 The cleanroom classification standards FS 209E and ISO 14644-1 require specific particle count measurements and calculations to classify the cleanliness level of a cleanroom or clean area. This paper compares the requirements of the two cleanroom classification standards and the implementation of the standard calculations in Particle Vision PortAll software from Pacific Scientific Instruments. Using measurement data from Met One or Royco particle counter instruments, the PortAll software can automatically generate cleanroom classification results. Summary of FS 209E and ISO 14644-1 and -2
Requirements for Classification Calculations Using PortAll The History and Future of ISO Cleanroom Standards
Federal Standard 209E has long been the only definition of cleanroom classification levels available from a standards organization. FS209E, Airborne Particulate Cleanliness Classes in Clean Rooms and Clean Zones, is from the U.S. General Service Administration and approved for use by all U.S. agencies. In the absence of an international standard, FS 209E was broadly used internationally. The need for a new international standard that covered more cleanroom environmental parameters and practices led to the formation of a technical committee of the International Standards Organization. The technical committee is named, ironically, TC 209 Cleanrooms and Associated Controlled Environments. The goal of TC 209 is "standardization of equipment, facilities, and operational methods for cleanrooms and associated controlled environments. This includes procedural limits, operational limits and testing procedures to achieve desired attributes to minimize micro contamination." This ISO committee will produce 10 new standards documents that relate to cleanrooms or clean zones (described below). The first two standards have been published: ISO 14644-1 and -2. The first document, ISO 14644-1, Cleanrooms and associated controlled environments Part 1: Classification of airborne particulates has been released as a final draft international standard (FDIS). The second document, ISO 14644-2, Cleanrooms and associated controlled environments Part 2: Testing and monitoring to prove continued compliance with ISO 14644-1; has been released as a draft international standard (DIS). Both are legal for use in trade. By U.S. law, FS 209E can be superseded by new international standards. It is expected that 209E will be in use in some industries through the next five years, but that eventually it will be replaced globally by ISO 14644-1. Particle Vision PortAll software performs the cleanroom classification calculations for airborne particulate levels required by both of the U.S. and ISO standards. The actual text of the standards must be ordered from the appropriate standards organization (see Sources and Links). This paper gives a general overview of the required particle count measurements given in the standards.
Summary of FS 209E and ISO 14644-1 and -2 The cleanliness classification levels defined by FS209E and ISO 14644-1 are approximately equal, except the new ISO standard uses new class designations, a metric measure of air volume and adds three additional classes - two cleaner than Class 10 and one beyond than Class 100,000. The second new ISO standard, ISO 14644-2, gives requirements for monitoring a cleanroom or clean zone to provide evidence of its continued compliance with ISO 14644-1. The following table compares FED STD 209E to the new ISO 14644-1 classifications.
The ISO standard also requires fewer sample locations, especially as the cleanroom/area size increases; however, the ISO standard does require minimum one minute samples, whereas the Federal Standard allows shorter samples, especially at smaller particle sizes. For example, to certify an FS Class 10 cleanroom (ISO class 4), with 250 square feet (7.08 square meters), classified at 0.3 micron with a 1 cf/m flow rate particle counter, the required number of sample locations, sample volumes, and sample times would be as follows:
The precise count levels required by ISO 14644-1 for each classification, by particle size, are given below.
ISO 14644-2 determines the type and frequency of testing required to conform with the standard. The following tables indicate which tests are mandatory and which tests are optional.
There are three basic steps to classifying a cleanroom using a particle counter and Particle Vision PortAll software:
Although the FS and ISO standards can seem complicated, once you have determined the required number of samples for your cleanroom/area and mapped their locations, you will repeat the same samples at the same locations each time you re-certify the cleanroom. PortAll software automatically performs the calculations and gives the results. All you have to do is collect the sample data. Procedures for each of the standards are described below.
Basically, the ISO requirements are as follows:
Detailed step-by-step descriptions of the requirements are given below. To determine the number and type of particle count samples for your cleanroom/area required by the ISO standard, the following basic information is needed:
1. The minimum number of sample points is calculated as follows:
2. The minimum sample volume at each point is obtained as follows:
Vs = ( 20 / Cn,m ) x 1000 Where : Vs is the minimum sample volume, in liters Cn,m is the class limit (in number of particles per cubic meter for a given particle size) Note: if you intend to calculate the class level at multiple particle sizes, be sure to select a sample volume for the largest size, which is also the largest required volume. This will ensure the sample data is valid for all sizes. 3. The minimum sample time at each location must be one minute or greater. 4. There is no definition of the number of samples to be taken at each sample point except in the case when there is only one sample point. For one sample point, there must be at least three sample volumes taken. Note: PortAll software requires at least two locations to perform classification calculations, making the last requirement irrelavent. Once the samples have been collected, connect the particle counter to the PortAll computer's serial port and the software will read the data from the particle counter memory and display the data in a spreadsheet. Select the sample count values to be used in the classification calculation. (The classification level can only be calculated for one particle size at a time.) Click the ISO calculator icon to perform the classification calculations. The resulting classification for the selected particle size is displayed at the bottom of the sample data for that size column on the spreadsheet. Per the ISO standard, if the number of sample locations is greater than 10 and more than one sample was collected per location, then the classification is determined by the averages of the particle counts obtained at each location. The calculated average at each location must pass the classification limit. If the number of sample locations is at least two but not more than nine, then the Upper Confidence Limit [UCL] will also be calculated, and the calculated value for the UCL must also be less than the classification limit.
Basically, the Federal requirements are as follows:
Detailed step-by-step descriptions of the requirements are given below. To determine the number and type of particle count samples for your cleanroom/area required by the Federal Standard, the following basic information is needed:
1.The minimum number of sample locations varies based on the flow type. A) For unidirectional flow, the minimum number of locations is calculated by:
B) For non-directional flow, the minimum number of sample locations is calculated by:
2. The minimum sample volume at each point is obtained by the larger of:
Vs = (20 / Cn,m )x 1000 Where Vs is the minimum sample volume, in liters Cn,m is the class limit (in number of particles per cubic meter) 3. There is no minimum sample time at each location. 4. There is no definition of the number of samples to be taken at each sample point except that at least five sample volumes must be taken in each cleanroom/area being classified. Once the samples have been collected, connect the particle counter to the PortAll computer's serial port and the software will read the data from the particle counter memory and display the data in a spreadsheet. Select the sample count values to be used in the classification calculation. (The classification level can only be calculated for one particle size at a time.) Click the FS209 calculator icon to perform the classification calculations. The resulting classification for the selected particle size is displayed at the bottom of the sample data for that size column on the spreadsheet. Per the FS209E standard, if the number of sample locations is greater than 10 and more than one sample was collected per location, then the classification is determined by the averages of the particle counts obtained at each location. The calculated average at each location must pass the classification limit. If the number of sample locations is at least two but not more than nine, then the Upper Confidence Limit [UCL] will also be calculated, and the calculated value for the UCL must also be less than the classification limit.
Requirements for Classification Calculations Using PortAll Once you have selected the count values in the spreadsheet for the particle size you want used for the classification calculation, PortAll calculates the class as follows: PortAll searches the unselected region of the spreadsheet and determines the number of sample locations involved. The software then sorts the samples by location and determines the average count value per location. The highest average count value is determined and this value is compared to the standard table to determine the classification. If there are between two and nine locations, PortAll also calculates the UCL and compares the result to the standard table. The UCL result and average count result are compared and the worst classification is chosen. The following four rules must be followed to ensure an accurate classification result from PortAll.
Note: Sometimes it is helpful to clear the instrument memory before beginning a sampling sequence to classify a cleanroom/area. This ensures that the PortAll spreadsheet of the instrument memory will only contain relevant samples, making it easier to select which data should be used for the classification calculations.
The History and Future of ISO Cleanroom Standards In 1992, at the urging of the Institute of Environmental Sciences, the American National Standards Institute petitioned ISO to create a technical committee on cleanrooms and associated controlled environments. This new committee, ISO TC 209, was formally established in May 1993. Its mission is to develop an international standard for cleanrooms and associated controlled environments that encompasses the standardization of equipment, facilities, and operational methods, while also defining procedural and operational limits and testing procedures to minimize contamination. Thirty-four countries are currently active in ISO TC 209. Voting members are Australia, Belgium, China, Denmark, Finland, France, Germany, Italy, Jamaica, Japan, Korea, The Netherlands, Norway, Portugal, Russia, Sweden, Switzerland, the United Kingdom, and the United States. Nonvoting members are Bulgaria, the Czech Republic, Egypt, India, Ireland, Malaysia, New Zealand, the Philippines, Poland, Saudi Arabia, South Africa, Thailand, Turkey, Ukraine, and Yugoslavia. Two Draft International Standards (DIS) have been released by the committee: ISO/DIS 14644-1, Cleanrooms and associated controlled environments-Part 1: Classification of airborne particulates, and ISO/DIS 14644-2 Cleanrooms and associated controlled environments-Part 2: Specifications for testing and monitoring to prove continued compliance with ISO 14644-1. These first ISO cleanroom standards are two of 10 documents (see table A) that will make up the new family of global cleanroom standards. Many of these documents are at the final voting stage and can be legally used in trade.
ISO/FDIS 14644-1 Classification of Air Cleanliness ISO/DIS 14644-2 Cleanroom Testing for Compliance ISO-14644-3 Methods for Evaluating & Measuring Cleanrooms & Associated Controlled Environments This document describes the necessary performance tests for various types of cleanrooms. The occupancy states of "as built", "at rest", and "in operation" are defined as well as appropriate levels of certification. A large index is provided on a variety of test methods and appropriate equipment. ISO-14644-4 Cleanroom Design & Construction This document will be a primer on the design and construction of cleanrooms. It will cover all aspects of the process from design development to startup and commissioning. ISO-14644-5 Cleanroom Operations This document will be a primer on cleanroom operation. It will cover all aspects of the operation of a cleanroom including entry and exit procedures for equipment and personnel, education and training, cleanroom apparel, and facility issues such as maintenance, housekeeping, monitoring, system failure, etc. ISO-14644-6 Terms, Definitions & Units This document will provide a consistent reference for all terms, definitions and units discussed across all ISO cleanroom standards. ISO-14644-7 Enhanced Clean Devices This document will focus on specialized stand-alone clean spaces including their design, construction, and operations. ISO-14644-8 Molecular Contamination This will be a new document covering measurement of airborne molecular contamination in clean zones. The first meeting is scheduled for December 1998. ISO-14698-1 Biocontamination: Control General Principles This document describes principles and basic methodology for a formal system to assess and control biocontamination where cleanroom technology is applied. ISO-14698-2 Biocontamination: Evaluation & Interpretation of Data This document describes basic principles and methodology for microbiological data evaluation. It provides a method of estimating of biocontamination from sampling for viable particles in zones at risk. ISO-14698-3 Biocontamination: Methodology for Measuring Efficiency of Cleaning Inert Surfaces This document outlines the methodology to measure the effectiveness of cleaning and/or disinfection of inert surfaces having biocontaminated wet soiling or biofilms. Listed below are ISO TC 209's seven working groups and their missions. Working Group 1 ISO 14644-1, "Classification of Air Cleanliness" Three new classes have been added to the existing standard, Federal Standard 209, two cleaner and one dirtier. ISO 14644-2 covers specifications for testing and monitoring. This document specifies the requirements for monitoring a cleanroom or clean zone to provide evidence of its continued compliance with ISO 14644-1 for the designated classification of airborne particulate cleanliness. A schedule of normative and informative tests is included in the document. Working Group 2 ISO 14698-1, "Biocontamination Control General Principles". This document describes the principles and basic methodology for a formal system to assess and control biocontamination. It will include the general requirements of a sampling plan; target, alert, and action levels; qualification; and reporting. ISO 14698-2, "Evaluation and Interpretation of Biocontamination Data." This document describes the basic principles and methodological requirements for all microbiological data evaluation and the estimation of biocontamination data obtained from sampling for viable particles. It will also include evaluation of the initial monitoring plan and of the data resulting from routine monitoring, as well as analysis of the data, trending, and record keeping. Working Group 3 A working group on metrology and testing methods. Performance tests are specified at operational phases—as-built, at-rest, and operational. The items to be measured are categorized as either primary or user-optional tests. Primary tests include particle count, airflow velocity, airflow volume, pressure differential, and installed filter leakage. User-optional tests include flow visualization, airflow parallelism, airflow turbulence, temperature, humidity, molecule contamination, electrostatic charge, particle fallout, recovery, and integrity. Working Group 4 ISO 14644-4, "Design and Construction." This document specifies requirements for the design and construction of cleanroom and clean air devices, as well as requirements for start-up and qualification. It also provides guidance on the basic elements of design and construction. Working Group 5 A cleanroom operations working group. Topics to be addressed include entry/admittance, procedures, and cleaning, as well as maintenance as it relates to equipment, materials, and people. Working Group 6 In detailing terms, definitions, and units, the definitive document of this working group must include all definitions from all approved documents of ISO TC 209. Consequently, it will be the final ISO TC 209 document. Working Group 7 The Enhanced Clean Devices working group.
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Document P/N 2084056 Written by Scott Hjelmervik, Software and Systems Manager, and by Joe Gecsey, Airborne Products Manager Copyright by Pacific Scientific Instruments Company, January 1999. All Rights Reserved. Specifications subject to change without notice |
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