With OSHA and CSA requirements for flame-resistant PPE apparel to mitigate arc flash risks, several cleanroom fabrics and garment system designs have come to the market. Flame-resistant cleanroom fabrics differ from traditional cleanroom fabrics in many ways. Because polyester tends to melt upon exposure to flame, cleanroom FR fabrics are made from filaments such as DuPont Nomex fiber. The Nomex filament for cleanroom applications is specifically engineered, and is not intended to shed fibers in the same manner as traditional Nomex. These fabrics must meet NFPA 70E ATPV ratings for arc flash protection while satisfying the stringent contamination-control requirements of the most demanding cleanroom environments.
Though destructive product testing demonstrates the PPE characteristics of these fabrics and garment systems, are they fit for stringent cleanroom use? One cleanroom laundry decided to find out. Extensive washing, drying, and particle and fiber testing were used to investigate whether cleanroom FR garments truly belong in a cleanroom gown room.
Recently, this cleanroom laundry provider found that customers needed to purchase a considerable quantity of cleanroom FR garments to fulfill their risk assessments and job hazard analysis, and to meet regulatory requirements for arc flash protection. Though these types of products are not entirely new, and in fact have been available for several years, the laundry could find little or no data to demonstrate the actual cleanliness or shedding attributes of the garment system, especially for use in ISO 3 or ISO 4 cleanroom environments. If these garments were now to be used in customers’ cleanrooms, contamination-control engineers would have to be satisfied as to their overall compatibility with their production environment. Thus, the garments would have to be cleanroom-laundered and tested through multiple iterations to measure their particle- and fiber-shedding potential.
The laundry set out to design a trial that would document all of the environmental impacts of garment processing and then test for particle and fiber release. To gather the most useful information and assess potential variations in shedding, the laundry decided to test not only FR garments but also traditional continuous-filament polyester cleanroom apparel.
The trial used five cleanroom FR coveralls that were washed, dried, and tested a minimum of five times each. The coveralls were made of DuPont Nomex fiber, with carbon filament to enhance ESD properties. The garments were manufactured using cleanroom garment standards, though with FR-compatible findings and construction methods. The garments were laundered in an ISO 4 cleanroom laundry with dedicated pass-through washers, using a wash formula with only cleanroom-filtered non-ionic detergent, and 0.2 micron verified RO/DI water maintained at 18 megohm, for all formula steps. The garments were tumbled dry in dedicated stainless, HEPA-filtered dryers, fitted with remote airborne particle counters continuously counting 0.3 µm particles. (As per the laundry’s quality criteria, empty dryers must have particle counts of less than 100 particles at 0.3 µm, before use.)
The garments were then tested in a dedicated ISO 4 analytical lab area, adjacent to the cleanroom folding area of the primary ISO 4 cleanroom. Garments were tested using ASTM F51: Standard Test Method for Sizing and Counting Particulate Contaminant In and On Clean Room Garments, and the Helmke Drum Test method as outlined in IEST-RP-CC003.4: Garment System Considerations for Cleanrooms and Other Controlled Environments. The test methods differ greatly, and no real correlation can be made between the two methods. Because the trial hoped to measure both the potential for shedding of particles and fibers, both test methods were required.
The primary considerations of the two test methods are as follows. ASTM-F51 measures particles at 5.0 µm and larger, plus fibers, while the Helmke Drum Test measures particles equal to or greater than 0.3 and 0.5 µm. The challenge for the trial would be that the garments meet the Class A classification of ASTM F51, and the Category 1 classifications of the Helmke Drum Tests. To meet the Class A classification of ASTM F51, the garments would have to shed fewer than 999 particles larger than 0.5 µm, and less than 10 fibers, for 0.1 m2 of fabric. For the garments to meet the Category 1 classifications of the Helmke Drum Test, a coverall would have to shed fewer than 2,000 particles of 0.3 µm and larger, per min, and 1,200 particles of 0.5 µm and larger, per min.
The continuous-filament polyester coveralls were laundered and tested using the same wash formula and equipment, and under the same conditions, as the FR garments. The garments provided were tagged with RFID chips for identification during the laundry process, as per routine production practices for this cleanroom laundry facility.
The FR garments had not been previously cleanroom-processed before the trial. The polyester garments, though relatively new, had been in use for about a month, but had seen very little use as per RFID incoming soil scans of the garments. All garments were thoroughly inspected before washing and testing, to ensure that there were no tears or anomalies that might skew the test results. The trial ran for several days to capture the unusually large number of data points, especially with the laborious test method of ASTM F51.
The initial belief at the inception of the trial was that the FR garments would shed relatively high amounts of both particles and fibers, and would shed somewhat more than the continuous-filament polyester garments. Though the FR garments did start off with elevated shedding, none of the trial garments exceeded the USL of the Class A classification of ASTM F51, or the Category 1 classifications of the Helmke Drum Tests. Additionally, repeated washing and drying demonstrated even less particle and fiber shedding – a pattern that is not atypical of polyester garments.
When compared with the polyester garments, the FR garments also performed well, showing comparable results during the trial. Though this trial fails to document the longevity and associated variables of continued processing to the perceived industry standard of 100 replicates for typical cleanroom garments, it does demonstrate that, at least at the outset, FR garments designed for cleanroom use do belong in the cleanroom.
1. ASTM F51: Standard Test Method for Sizing and Counting Particulate Contaminant In and On Clean Room Garments.
2. IEST-RP-CC003.4, Garment System Considerations for Cleanrooms and Other Controlled Environments.
Robert Nightingale is the founder and president of Cleanroom Garments. He has more than 20 years of experience in human source contamination and cleanroom apparel processing, with multiple cleanrooms supporting a vast array of applications from aseptic fill operations, aerospace, and MEMS fabrication, to automotive paint spray operations. Robert is also a co-owner of several international patents for cleanroom soil-removal processes, and currently consults to MSR-FSR Cleanroom Garment Solutions, with ISO 4 cleanroom facilities in Albuquerque, N.M., and Hillsboro, Ore.
This article appeared in the January 2013 issue of Controlled Environments.