Class and Particle Concentration RPs Revamped by IEST
11/01/1999
OAK BROOK, IL—Updating recommended practices and making them more user friendly are just some of the goals many chairpersons have for this month's working group sessions at the Institute of Environmental Sciences and Technology's (IEST) Fall Conference.
WG-CC100: Fed-Std-209: Airborne particulate cleanliness classes in cleanrooms and clean zones (Fed-Std-209) is one of 19 working groups scheduled to meet during the conference in Oakbrook, IL, November 15 through 17. Also slated for discussion are a host of recommended contamination control practices, including testing cleanrooms filters (both HEPA and ULPA), cleanroom design considerations, and garment system considerations.
"We can get into more detail with recommended practices than ISO standards, and we try to make them more user friendly," says David C. Swinehart, who chairs WG-CC100 for the Fed-Std-209 as well as WG-CC006: Testing Cleanrooms.
 We want more specific, meaningful tests. |
Although the similar ISO 146144-1-2 standards are descendants of the Fed-Std-209 standard, the differences in how particle concentration is calculated as well as cleanroom classification has created some confusion in the industries that adhere to these mandates. [See "The coming debut of ISO cleanroom standards," CleanRooms, April 1999, page 10; "Verifying a cleanroom classification," May 1999, page 9; "The UCL paradox in the cleanroom standards," June 1999, page 10.]
"Although both are based on the same technology, there are some differences in how clean air is classified," Swinehart explains. "The exponent has changed in the formula, and what the equation does in the federal standard is it allows a greater concentration for large particles and smaller concentration for small particles." The working group's goal, he adds, is to review the ISO standard and to recommend how the federal government should proceed with the standard.
CleanRooms columnist Bob Donovan, a process engineer, believes the working group should recommend an updated version of 209E, perhaps a 209F, that would be consistent with the ISO standard. "I am in favor of a 209F that retains the format of 209 with changed class definitions that would be identical to ISO standard and that uses the same nomenclature," he says. "I suspect that will not happen, even though it would not be a very onerous task."
There is an argument on the merit of both standards, Donovan says, adding that the ISO standard is easier to read and brief, while the 209 contains more detail. "Changing the nomenclature would be the easy part, but changing the process and verification is another matter," he says. "There are many people engrained in the federal standards, and upgrading 209E to 209F would be easier than asking people to adhere to the ISO standard."
Aside from the 209 standard, Swinehart says the testing cleanrooms recommended practice, RP-CC006, will undergo a "fairly extensive revision."
"We're trying to bring it up to current testing standards. There's a need for changes in test methods and there are some things in there that just aren't germane anymore," he adds.
The relevance of tests and methodology for garment systems is just what WG-CC003 will examine and rewrite to be more precise, says Chairman Charles W. Berndt. "We think the current recommended practice is outdated, and the problem is that tests that are available for measuring particles, fiber on garments as well as the filtration efficiency of fabric are outdated," says the CleanRooms Editorial Advisory Board member. "We want more specific, meaningful tests, and we will consider new tests."
Berndt also chairs WG-CC029: Automotive Paint Spray Applications, which released an updated, recommended practice earlier this year. [See "Paint spray practices released," CleanRooms, July 1999, page 4.]
Another recommended practice released earlier this year addresses HEPA and ULPA filter leak tests. R. Vijayakumar, chairman of standards and practices for the IEST, also serves as acting chairman of WG-CC034. The committee's newly published document simplified the practice, as leak tests for HEPA and ULPA filters were once topics in three separate recommended practices, including RP-CC002: Laminar Flow Clean-Air Devices.
Last year, Bruce McDonald, chairman of WG-CC002, pulled together leak testing procedures from RP-CC001, -CC002 and -C006. "I brought that first draft in and there were three or four meetings before it was published in July," he says. "Working group 34 went through and fixed it up."
And even though the recommended practice for HEPA and ULPA filter testing is relatively young, it is not finished. In fact, the RP is slated for updates at the fall conference. "We are already going to start revising it," Vijayakumar says.
Adds McDonald, "From the beginning, we realized it wasn't the final answer to this practice, but it was important to publish what we had. Leak tests varied between the documents, which duplicated effort and caused some confusion."