The well-dressed cleanroom
08/01/2008
By Bruce Flickinger
End users need to juggle product and worker protection, comfort, utility, and cost-effectiveness in making the right choices about specialist laundries and cleanroom garmenting programs.
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Any tailor will tell you that the signs of quality clothing can be found in the details, and the same can be said of cleanroom garments. In this analogy, companies such as Nitritex Ltd. (Newmarket, UK) are the high-tech haberdasheries, manufacturing cleanroom garments and apparel items to very high technical standards for customers operating a variety of demanding research and manufacturing environments.
“The construction of the garment is extremely important to ensure its effectiveness when worn in the cleanroom,” says Richard Bryant, Nitritex group sales director. “The fabric needs to be chosen carefully and be thoroughly technically specified to ensure it does not cause contamination in the finished garment. Each component–studs, thread, fabric, zippers–should be non-linting and made of non-plated stainless steel. Seams should be enclosed using continuous polyester thread at no less than 12 stitches per inch.” Garment edges usually are serged; that is, chain-stitched using two or more threads that form an overcast edge on a fabric.
Despite many advances in construction and fabric technology, the primary objective for cleanroom garment systems remains unchanged: to capture and entrain particles to prevent them from being dispersed externally and making contact with equipment or product. These contaminants largely are generated by the human body, including bacteria and yeasts, hair, dead skin cells, dandruff, and even elements such as sodium, potassium, chloride, and magnesium. It bears repeating here that people are the most significant source of contamination in cleanrooms and ancillary facilities.
But people also need to be protected, and a second but equally important function of cleanroom apparel is protecting workers from hazardous materials.
Risk assessments are used to ascertain the types and degree of worker protection required in a particular environment. Chemical splash protection is often needed, and difficult-to-control chemical flow or vapor eruption might warrant additional protection in some environments. Additionally, fire resistance is a concern for some applications, and awareness is heightened about OSHA/NFPA 70E requirements for protecting workers against potential arc flash events.
“The correct garment type is determined by the applicable technical standard, the type of cleanroom being operated, and the kind of work being carried out,” Bryant says. “We often provide on-site surveys to establish the correct garment type, along with training to assist wearers with the correct donning procedures to ensure that they adhere strictly to GMPs [Good Manufacturing Practices].”
Fabric options and tradeoffs
Garment considerations vary somewhat between industrial and life science cleanrooms. The former generally do not have a defined standard to work toward when choosing garments and must make the selection based upon the grade of cleanroom required or level of air cleanliness as defined by international standard. The life science or biopharmaceutical cleanroom, however, will have a more rigidly defined requirement for cleanroom clothing and its use as stipulated by GMP.
“Garments used in controlled environments share many common characteristics, such as compatibility with industrial laundering processes and low-particulation fabrics,” says Greg Winn, general manager, Controlled Environments Division, at White Knight Engineered Products (Charlotte, NC). “Carbon-grid fabrics are more commonly used in microelectronics applications because these customers will go to great lengths to control static buildup and/or discharge events. Pharma/life science customers must often maintain aseptic manufacturing conditions, so garments and materials undergo additional gamma sterilization or autoclaving procedures, which can significantly reduce material lifetime.”
Across all applications, key garment performance properties include air permeability, particle barrier efficiency, antistatic behavior, and moisture vapor transmission rate (MVTR). These speak broadly to a garment’s ability to both contain particles and keep the wearer comfortable. While all cleanroom garments need to meet technical specifications with regard to these properties, performance levels will vary and users need to assess carefully what criteria need to be emphasized while potentially compromising others.
An example is giving proper attention to worker comfort and mobility, which not only allows workers to carry out their duties throughout the day but also encourages compliance to the garment program. Cleanroom garments must permit the body to breathe, but the fabric’s breathability walks a fine line between comfort and contamination prevention: The body’s normal cooling process must be accommodated, but the airflow generated contains contaminants that can be transferred to the process or product. Lower MVTR and air permeability measurements mean lower potential for contamination but also reduced comfort for the wearer.
The fabrics used in making cleanroom apparel are largely polyester-based or 100 percent polyester weaves. Carbon matrices are used in some fabrics, and nylon and non-woven polyethylene materials are used in some special-purpose garment systems. The polyester weaves used in cleanroom garments are both hydrophobic and oligophilic and are constructed of very fine, tightly woven fibers. This creates small pore sizes for entraining skin flakes and other particles.
Sterilization, particularly gamma processing, will break down any fabric fiber to some extent. Polyester fabrics also are easily abraded by rough surfaces and are sensitive to extreme levels of acid or alkali and temperatures above 160??F. Manufacturers work continually to improve the expected life of reusable cleanroom garments by improving the technology and yarns used in the weave.
Manufacturing techniques also are constantly being improved. One example is Laser Serge®, White Knight’s proprietary fabric cutting technique developed as an alternative to serging raw edges. The process creates a precise, laser-fused garment edge that is consistently sealed and highly resistant to fraying, even after multiple washings. The laser source simultaneously cuts and seals to accuracies within ??0.03 mm. “LaserSerge prevents unraveling of fabrics and maximizes material usage,” Winn says.
“We currently use LaserSerge for product development and precision pattern/marker operations to validate concepts,” he continues. “Automation software allows us to run thousands of iterations in seconds to achieve optimum efficiency and utilization before ever cutting the fabric.”
The equipment piece
While the polyester fabrics used in contamination-control environments are durable and do not readily fray or generate lint, they can be challenging to clean. Laundering cleanroom garments is not a straightforward affair, and only the very largest cleanroom operators consider running their own laundry. Those that do might enlist the services of UltraClean Laundry Equipment (Cloudcroft, NM), a manufacturer of cleanroom dryers and washer extractors. The bulk of the company’s customers are ISO Class 3, 4, 5, and 6 cleanroom laundries.
“Our primary client base consists of full-service garment suppliers that typically offer gown rental, processing, and garment repair along with complementary cleanroom services,” says Mark Horton, general manager at UltraClean Laundry Equipment. “We also serve end users with on-premises laundries, which usually are companies that use 2,000 or more gowns per week or have special gown processing requirements.”
Horton notes that ISO classifications 1 through 4 require ultrapure deionized water for garment laundering, “so 316 stainless-steel construction is required on all wetted surfaces.” Air control is also important because the washer breathes during loading, unloading, and washing. For dryers, the ISO standards entail continuous design improvements to reduce all potential contamination sources during the life of the dryer.
“Ionization [to neutralize static electricity buildup], humidity-sensing drying controls, and networked real-time reporting have become more common on cleanroom dryers,” Horton says. UltraClean’s dryers also feature built-in particle counters (optional) and a Turbo Box that connects to the blower inlet to maintain air velocity that eliminates particle drop-out.
The company’s pass-through washer/extractors allow soiled laundry to be loaded from one side and clean laundry to be unloaded in the cleanroom. All wetted parts are 304L or 316 stainless steel, and units feature microprocessor control, a liquid supply interface, and programmable deionized water use. Dryers have stainless steel for all wetted parts and come complete with HEPA filter systems.
“Most customers require QA documentation from us and proper training for their operators,” Horton says. “The primary test is to take particle counts inside an operating dryer. Temperature sensors are normally calibrated, and with current energy costs, it is more important than ever to program dryers to not over-dry the garments.”
UltraClean offers up-front engineering support for infrastructure considerations such as air/water supply and in selecting cleaning
insing solutions. “We provide operator training during equipment commissioning and can offer advice regarding ultrapure deionized water usage, the need for ultraviolet treatments, minimum flow rates, chemical dispensing, sourcing, typical wash and dry formulas, and so on,” Horton says.
Disposable or reusable?
Contracting with a specialist laundry and reusing garments is the most sensible option for many cleanroom operators. End users commonly rent garments from a supplier, which provides all laundering and testing services for the garments. Few companies actually own their garments, and fewer still operate their own laundering facilities. “The key drawback of purchasing garments is the initial cost and subsequent replacement or increase of garments, which can be significant,” says Jan Eudy, corporate quality assurance manager with Cintas Corp. (Cincinnati, OH).
Eudy points to several other advantages to renting garments: All auditing and validation of fabric and garment manufacturers has been performed and documented to assure the highest quality and durability of the cleanroom garments. All size changes, additions, and deletions are included in the program, so there is better control of inventory levels.
Bryant of Nitritex notes these considerations in deciding whether to rent or purchase garments: “The number of wearers, how often they change garments and whether the customer has a constant requirement for a number of garments per week or if they have peaks and troughs in their usage. The frequency with which workers are required to change their garments is highly variable across different companies.
“Although some end users purchase garments and wash them in their in-house laundries, these facilities generally do not process to the same standard as the specialist laundries,” he adds.
For specialist laundries, “A recent trend I see is potential customers asking for more up-front quality assurance information before contracting for services,” says Lori Uram, quality assurance manager with ARAMARK Cleanroom Services (Downers Grove, IL). “Our current and potential customers frequently audit our operations and require quality assurance compliance documentation from us, particularly for regulatory audits.”
Most laundries also provide customer tracking mechanisms and garment usage information that help identify potential problems and opportunities for cost savings. Customers contracting with ARAMARK, for example, can access its Cleantrak™ system, a real-time, web-based tool that “provides end-user paperwork so a customer will know in advance what items will be delivered, and also provides current and historical information on ruined garments down to the individual barcode,” Uram says. Other data include type and number of repairs performed, unreturned garments, shortages and overages by size and item, and average garment age. “Cleantrak virtually eliminates the opportunity that garments could potentially be lost and identifies poor FIFO on the part of the customer,” she says.
Disposable garments are a viable option for some users and applications. Horton says disposables make sense in many ISO Class 6 operations and those that are not conducive to garment cleaning, such as nuclear, some types of food processing, and some pharmaceutical applications. Disposable garments also might make sense for companies that have low gown usage requirements, and they are recommended in biohazardous critical environments (BSL-2, -3, and -4 cleanrooms) and heavy soil applications such as preventive or corrective maintenance of equipment in the cleanroom, according to Eudy.
Uram adds, “Disposables are preferred whenever an employee is working with something that cannot be removed or inactivated from the garment. It is safer to throw the disposables out.”
Garment integrity and replacement
One issue with reusable cleanroom garments is that they deteriorate over time due to wear, laundering cycles, and sterilization. It is important to know when to replace them. Less critical industries might rely on a visual evaluation of the garment or the number of launder cycles to determine when garments need to be replaced, but most specialist cleanroom laundries validate their processes for at least 100 launder cycles. This equates to roughly five or six years of life for a garment, depending upon the laundry’s annual processing cycle.
The testing involved in this validation, as well as in all performance testing for cleanroom garments, is codified in IEST-RP-CC003.3. First published in 2003 and titled “Garment Considerations for Cleanrooms and Other Controlled Environments,” the document is a resource for determining the fabric; garment system and configuration; and cleaning, maintenance, and testing regimens for aseptic and non-aseptic cleanroom applications.
The recommended practice incorporates American Society for Testing and Materials (ASTM) and American Association of Textile Colorists and Chemists (AATCC) test methods. These methods (and their applicable standards) include weight (ASTM-D-3776), thickness (ASTM-D-1777), grab tensile (ASTM-D-1682), MVTR (ASTM-E-96B), air permeability (ASTM-D-737), pore size (Coulter porometer), abrasion resistance (Wyzenbeek/Taber), Suter hydrostatic pressure test (AATCC-127), spray rating (AATCC-22), flammability (ASTM-F-1506, 16 CFR Part 1610, NFPA 70E), surface resistivity (ASTM-D-257, AATC-76), static decay (FTM 4046), and bacterial filtration efficiency (modified Ford Peterson Method).
Additionally, several tests are available to test garment particle shedding and containment. The “body box,” or particle containment test, evaluates the entire cleanroom garment system in a simulated cleanroom environment. The background particle load of the area first is determined by standard measurement. A worker inside the box wearing the garment system to be tested then performs a series of prescribed movements to the cadence of a metronome. The particle measurement during this activity determines the garment system’s filtration and particle containment efficacy.
The Helmke Tumble test also is used to assess an entire garment for shedding of particles from 0.3 to 10 μm. ASTM F51 (“Alternate Method, Standard Test Method for Sizing and Counting Particulate Contaminant In and On Cleanroom Garments”) evaluates one square foot of fabric for shedding of fibers and particles 5 μm and greater.
Sophisticated supportive tests, such as SEM/EDX or SEM/EDS (scanning electron microscopy with energy-dispersive x-ray or energy-dispersive spectroscopy) can be performed to identify the particles generated from these tests as either soluble, insoluble, or ionic.
The test specifications set forth in RP-CC003.3 can be used to determine when the cleanroom garment should be replaced: A percentage change from the original test data can be used to objectively determine the replacement of the cleanroom garment. A garment should be replaced when one test criterion fails, Cintas’s Eudy says.
Specifications also should be set pertaining to the number of patches, staining, and sewing repairs made to the garment. The number and size of patches and stains permitted should be set by the user. Eudy offers this general guide: no more than three quarter-sized patches per garment item, sewing repairs no longer than 3 inches, and no stains larger than a credit card. Any repairs must be performed as specified by the fabric and/or garment manufacturer.
”Educating users on what constitutes garment damage and what they can do to prevent it is a key component of our quality assurance program,” ARAMARK’s Uram says. “We also alert operators to never throw a garment away even if it is damaged. This is a preventive measure we take to minimize the occurrence of loss and ruin.”
Don’t overlook undergarments
A well-constructed garment can only function to its optimum performance if it is used with undergarments specifically designed for cleanroom use. Cleanroom undergarments are a proven way to reduce the particulate and bioburden challenge on the outer cleanroom garments.
Advances in fabric technology allow undergarments to be made in very thin, low-shedding synthetic material with a high degree of wearer comfort while still providing an effective barrier for viable and non-viable contamination, Bryant says. The undergarments essentially act as a pre-filter for the outer garments.
“Many viable and non-viable particles are carried into the cleanroom on operators’ street clothes,” Eudy says. “Undergarments augment the containment of these particles when worn under coveralls, hoods, and boots in ISO Class 3, 4, and 5 cleanrooms.” She adds that cleanroom undergarments can be worn in ISO Class 6, 7, and 8 areas in lieu of frocks over street clothes.
“When worn correctly, these garments protect the cleanroom environment from contamination better than frocks worn over street clothes,” Eudy says. “The Cintas undergarment shirt and pant not only protect the product from particles, the fabric contains an ESD yarn to prevent particle migration due to electro-inductive forces.”
Nitritex’s Bryant adds that specialist laundry providers have been a major part of the undergarment validation for sterile cleanrooms and would always recommend the use of undergarments for sterile and aseptic applications. “While, in theory, all cleanroom operators should wear undergarments, economic considerations have to be part of the decision-making process in less critical applications,” he says.
Simple, practical programs
Garments and garmenting programs are a substantive cost center for most cleanroom operations, but Winn and others note that they are a manageable component of a company’s overarching contamination control program. “If you look at the costs of the entire contamination control program, garments will certainly be a cost factor but it is crucial that the contamination control procedures throughout are well planned and implemented with discipline,” Winn says.
Garment programs should be simple and straightforward for the operators to manage, for wearers to comply with, and for the laundry service to accommodate. Essentially, the program needs to strike a balance between limiting potential liabilities due to contamination from personnel while minimally disrupting day-to-day cleanroom productivity. Safety should also be encompassed in the program, through training, highly visible material safety data sheets, safety reminders, gowning order posters, and safety audits.
In addition to establishing gowning (donning and doffing) techniques and addressing behavioral/hygiene issues, a garment program should include baseline ionic extraction (ICP/MS, ESD, SEM/EDX), Helmke Tumble, and ASTM F-51 testing at the outset of the program’s implementation. This allows operators to assess both the particulate cleanliness of the garments and baseline particulate levels in the gowning areas. Ionic extraction testing should then be conducted routinely and the results trended so that any aberrations in the particulate load can be identified.
This way, operators can either identify or eliminate people, their garments, and gowning techniques as a contamination source in the event cleanroom performance becomes an issue. If the same garments have been used successfully for some time, the garment material probably is not particulating. “One possibility is that the garments are being returned from the cleanroom laundry in a contaminated state and this should also be checked,” Bryant says. “If these checks prove negative, then it is unlikely that the garments are causing the problem.”
Another check is measuring the particle count when the cleanroom is at rest (unmanned), Bryant adds. “If contamination is found, then this proves that it is from an external factor and is not caused directly or indirectly by the workers or their garments. The cause is then more likely to be damaged filters, faulty production equipment, or incorrect or insufficient cleaning.” Conversely, if contamination is bacterial as opposed to particulate, workers usually are the cause.
A cleanroom’s gowning requirements should regularly be assessed against ISO standards, OSHA requirements, and other applicable regulations, observers say. Even if a company’s production processes are stable, it is worthwhile to re-examine cleanroom garment systems and protocols to ensure that they are both in regulatory compliance and operating as cost-effectively as possible, based on currently available protective wear products.
Personnel working in the cleanroom are critical to the overall control of viable and non-viable particles, and they are always a potential source of contamination. “Education and awareness of personnel gowning practices and procedures may improve or maintain the particle cleanliness of the cleanroom,” Eudy says. “Well-trained cleanroom operators, especially those in aseptic environments, pay sufficient attention to garmenting issues.”
Resources and contacts
ARAMARK Cleanroom Services
Downers Grove, IL 888-648-7489 (North America)
800-759-0102 www.nitritex.com
www.aramark-cleanroom.com
UltraClean Laundry Equipment Co.
Cintas Corp. Cloudcroft, NM
Cincinnati, OH 888-267-5553
513-701-2200 www.ultracleanlaundry.com
www.cintas.com
White Knight Engineered Products Inc.
Nitritex Ltd. Charlotte, NC
Suffolk, UK 704-542-6876
+44-1638-663-338 www.wkep.com