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Cleanroom Arc Thermal and Flame Resistant Garments

I am a Production Supervisor working in an ISO Class 4 cleanroom in the semiconductor industry. The company Health & Safety Committee is requiring clean-room operators that perform maintenance on equipment in the cleanroom to wear protective garments that comply with NFPA 70E. What garments comply with cleanroom standards and NFPA 70E?

The task of creating compliance to multiple, divergent standards (cleanroom standards and safety standards) can be daunting. The implementation and execution of a cleanroom compliant program requires the cleanroom operators to wear a cleanroom compatible garment system (coveralls, hood, boots, and sometimes undergarments) constructed of 100% polyester to prevent contamination of the cleanroom and the products and processes in the cleanroom. However, when ignited, 100% polyester will melt and likely cause injury to the cleanroom operator/electrician 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. These garments will shed particles that will compromise the integrity of the cleanroom and contaminate the products and processes in the cleanroom. The FDA regulated industries mandate that ifthese garments are worn in a sterile cleanroom environment, they must be validated.

NFPA 70E
Compliance to NFPA 70E in cleanroom environments requires that all personnelworking on electrical equipment operating at >50V wear arc-flash protectivegarments to prevent injury. Polyester is specifically prohibited under any circumstanceswhen exposed to live electrical parts operating >50V. The automotive industryhas been using cleanroom FR garments meeting ASTM F1506 for workers exposed toelectric arc for several years in their cleanrooms and recently the pharmaceuticaland semiconductor industries have begun wearing these cleanroom FR garments intheir manufacturing cleanrooms.

Cleanroom FR Fabric
Dupont’s filament Nomex® is used to create the flame resistant characteristic in fabrics for cleanroom applications. Normal woven Nomex® yarn generates particles in the cleanroom, however the filament Nomex®used in cleanroom FR fabrics uses the same Nomex® chemical structure in a filament form to replace the fibrous forms used in most Nomex®fabrics. In most of the FR clean-room fabrics, filament Nomex® and carbon yarn is combined and woven into fabric. This resulting fabric is flame resistant, cleanroom compatible, and static dissipative. Allocation requirements to military garments and the Department of Defense have created a lower supply for domestic, commercial manufacture of cleanroom FR fabric. Many orders placed today for cleanroom FR garments may not be completed for six months but research and developmentis ongoing to find other compliant materials for cleanroom applications.

Construction of Cleanroom FR Garments
Typical cleanroom garments constructed of cleanroom FR fabric meet NFPA 70E Category 1. Seam construction of cleanroom FR garments must comply with IEST-RP-CC003.3 (i.e. 100% Nomex filament thread for sewing, serging of all rough edges and flat feld seams, etc.) to assure cleanroom compatibility, durability of the seams and encapsulation of particles. All other components (i.e. zippers with protective tape, protective snaps, tunnel-ized neoprene wrist closures, etc.) in the garment must be cleanroom compatible and flame resistant as well. Flame resistant cleanroom garments must meet ASTM F1506 and be labeledas such to meet NFPA 70E.

Validation of Cleanroom FR Garments
The validation of the cleanroom flame resistant garment system includes all the results of the tests performed to confirm cleanroom compatibility, gamma compatibility, and flame resistance. Testing of clean-room FR garments must be performed to validate arc-flash resistance per ASTM F 1959 to determine their arc rating. The sterility of the garment per ANSI/AAMI/ISO 11137-1994 over time must be validated in the FDA regulated industries as well as thedurability of flame resistance after many exposures of gamma radiation.

Compromise of Cleanroom Protocol and Flame Resistant Protection
If cleanroom operations require compliance to NFPA 70E Hazard/Risk Category (HRC) 2, a compromise of the two specifications must be weighed (increased contamination of the cleanroom versus protection of cleanroom operators/electricians). Some companies have chosen to provide flame resistant undergarments (FR cotton protective apparel) to wear under clean-room FR garments. However, these garments may be heavy, and operators often are uncomfortable wearing thesegarments for long periods of time.

Constant research and development of the construction of these garments and of meeting the compromises of wearer comfort, cleanroom compatibility, and flame resistance (both Category 1 and 2) characteristics is being conducted by fabric and garment manufacturers worldwide and new dual layer systems are available now which offer cleanroom compatibility and HRC2 compliance.

IEST Working Group 3 Subgroup
The IEST Working Group 3 that writes the recommended practice for cleanroom garments has created a subgroup to evaluate current industry best practices for cleanroom flame resistant clothing. Troy Ohmes (tohmes@wkep.com) is the Chairperson of this sub-committee. The next meeting of this working group is at ESTECH, the annual technical meeting of the IEST in Phoenix, AZ on May 8, 2006. For more information on flame resistant standards and arc flashyou may contact Hugh Hoagland co-chair ASTM Arc Flash Taskforce at hugh@arcwear.com.

Jan Eudy is IEST Past-President, serving this position from July 1, 2005 toJuly 1, 2006. She is also Corporate Q.A. Manager for Cintas Cleanroom Resources.

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