Flame and Arc Flash Protective Clothing in the Cleanroom
My company’s Health & Safety Committee requires all cleanroom operators that perform maintenance on equipment in the cleanroom wear protective garments that are arc flash PPE (personal protective equipment). What garments comply with cleanroom standards and NFPA 70E?
Hazard risk assessment
The task of creating compliance to multiple, divergent standards (cleanroom standards and safety standards) can be daunting. OSHA guidelines for PPE (personal protective equipment) are found in 29 CFR 1910.132.
When selecting cleanroom PPE one must consider:
• The ergonomics of working in the cleanroom
• Potential contamination of the integrity of the cleanroom
• Worker compliance with wearing PPE and wearing it correctly
• Worker heat stress with wearing of the PPE
• Slips, trips, or falls when wearing PPE
• Other regulatory compliance such as sterile PPE
The implementation and execution of a cleanroom compliant program per IEST-RP-CC003, Garment Considerations for Cleanrooms and Other Controlled Environments, requires the cleanroom operators to wear a cleanroom compatible garment system (coveralls, hood, boots, and sometimes undergarments) constructed of 99 percent polyester/1 percent carbon or 100 percent polyester to prevent contamination of the cleanroom and the products and processes in the cleanroom. However, when ignited the polyester-based fabric will melt and likely cause injury to the cleanroom operator if exposed to electric arc or flash fire. Traditional flame resistant clothing is constructed of flame retardant treated cottons or an inherently flame resistant material like DuPont Nomex® fiber that self-extinguish so as to limit (not eliminate) burn injury. These garments will shed particles that will compromise the integrity of the cleanroom.
The first step is to perform a hazard risk assessment per NFPA 2113, Standard on Selection, Care, Use and Maintenance of Flame-Resistant Garments for Protection of Industrial Personnel Against Short-Duration Thermal Exposures from Fire. Fire sources in cleanrooms can be flammable liquids, flammable gases, or flammable dust. This standard also addresses how to train operators how to wear these garments correctly and the laundering and maintenance of these garments. IEST Working Group 3 is finalizing a supplement to IEST-RP-CC003 to address these issues for cleanroom compatible and gamma compatible Arc Flash and Arc Rated (AR) garments. NFPA 2112, Standard on Flame-Resistant Garments for Protection of Industrial Personnel Against Flash Fire, will assist you in evaluating currently available reusable, industrial FR garment designs and characteristics.
Compliance to NFPA 70E, Standard for Electrical Safety in the Workplace (2015) in cleanroom environments, requires that all personnel working on electrical equipment operating at >50V wear arc flash protective garments to prevent injury. Polyester is specifically prohibited under any circumstances when exposed to live electrical parts operating >50V. The automotive industry has been using cleanroom compatible arc flash and arc rated garments meeting ASTM F1506 for workers exposed to electric arc for several years in their cleanrooms and recently all cleanroom industries have begun wearing these garments in their manufacturing cleanrooms. The 4th Edition NFPA 70E 2015 standard requires all arc flash PPE to be tested for arc thermal performance value (ATPV) to determine the category level. The Arc Flash PPE Category replaces the Hazard/Risk Category in previous editions of NFPA 70E. In the 4th Edition NFPA 70E standard, the term flame resistant (FR) is replaced by the term arc rated (AR). Arc rated clothing is also flame resistant.
Cleanroom arc flash AR fabric
DuPont’s filament Nomex® is used to create the arc flash and flame resistant characteristic in fabrics for cleanroom applications. Staple Nomex® yarn used in industrial clothing generates particles in the cleanroom; however the filament Nomex® used in cleanroom arc flash and arc rated fabrics uses the same Nomex® chemical structure in a filament form to replace the fibrous forms used in most Nomex® fabrics. The fabric does not ignite, melt, drip, nor continue to burn; maintains a barrier from flames and insulates the wearer from heat; and resists breaking open.
In most of these cleanroom fabrics, filament Nomex® and carbon yarn is combined and woven into fabric. This resulting fabric is cleanroom compatible, gamma compatible, static dissipative, and protective in the event of an arc flash or flash (short duration) fire. The specific tests that are performed on cleanroom polyester fabrics are also performed on cleanroom arc flash arc rated fabrics.
Construction of cleanroom arc flash AR garments
Current cleanroom garments constructed using cleanroom Nomex® fabric meet NFPA 70E Arc Flash PPE Category Level 1 or ATPV < 5.0 cal/cm2. Seam construction of cleanroom arc flash AR garments must also comply with IEST-RP-CC003 (i.e., 100 percent Nomex® filament thread for sewing, serging of all rough edges, and flat feld seams) to assure cleanroom compatibility, durability of the seams, and encapsulation of particles. All other components (i.e., zippers with protective tape, protective snaps, tunnelized neoprene wrist closures, and boot soles) in the garments must be cleanroom compatible, gamma compatible, and arc flash and flash fire resistant as well. These cleanroom PPE garments must meet ASTM F1506 and be labeled as such to meet NFPA 70E. The Particle Containment (Body Box) testing per IEST-RP-CC003, Garment Considerations for Cleanrooms and Other Controlled Environments, may be performed to evaluate the construction of the garment.
Compromise of cleanroom protocol and arc flash and flash fire protection
NFPA 70E requires that all PPE worn is based on the level of risk, therefore it is recommended that all cleanroom operators wear the two layers of cleanroom arc flash AR garments as stated above. Proper use of these garments mandates that they are worn correctly and are cleaned, inspected, and repaired correctly or removed from service. The recommended gowning protocol requires the cleanroom arc flash AR building suit top and bottom to be donned over all natural, non-melting underwear such as silk or cotton and worn under an additional layer of cleanroom arc flash AR garments. For compliance in ISO Class 6-8 cleanroom environments, a cleanroom arc flash AR frock is donned over the building suit top and bottom using recommended cleanroom gowning protocol or over industrial AR garments that meet NFPA 2112. A disposable Nomex® bouffant is worn under an AR balaclava or helmet and shield. AR gloves are donned to protect the hands and fingers. For compliance in ISO Class 3-5 cleanroom environments, a cleanroom arc flash AR coverall, hood, and boots are donned over the cleanroom arc flash AR building suit top and bottom using recommended cleanroom gowning protocol.
A disposable Nomex® bouffant is worn under the cleanroom arc flash AR hood. AR gloves and an AR shield are donned to protect hands, fingers, and face. This dual layer cleanroom arc flash AR garment system may be heavy, hot, and operators sometimes are uncomfortable wearing these garments for long periods of time in the cleanroom environments. However, constant research and development of the fabrics, components, and construction of these garments and of meeting the compromises of wearer comfort, cleanroom compatibility, gamma compatibility, and flame resistance (both arc flash PPE Category Levels 1 and 2) characteristics is being conducted by fabric and garment manufacturers worldwide which offer cleanroom compatibility and arc flash PPE compliance per NFPA 70E.
Must all cleanroom personnel who work in the cleanroom wear cleanroom arc flash AR garments? The answer is based on your company’s risk assessment and the standards cited in this article. IEST-RPCC003.5, which includes the cleanroom arc flash and arc rated garment supplement, will be available in late 2016.
The author acknowledges and thanks Jennifer Galvin of DuPont, Nathaniel Terry of Burlington Industries, Mark Miskie of White Knight Engineered Products, and Dan Campbell of Euclid Vidaro Mfg. Co. for their contributions to this article.
Jan Eudy is a Cleanroom/Contamination Control Consultant as well as a Fellow and Past President, Institute of Environmental Sciences and Technology. She is located in Carolina Beach, N.C., and can be reached at email@example.com.