Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 91 of 707

Figure: Typical adsorption cycle. EMISSIVE LOSSES/EXPOSURE LIMITS This past April, the EPA updated the NESHAP regulations concerning the levels of health hazards presented by certain solvents used primar- ily for vapor degreasers. These solvents were methylene chloride (MC), trichloro-ethylene (TCE), and perchloroethylene (PCE or Perk). These three solvents were the most commonly used remaining solvents covered by NESHAP. This update will affect some solvents users con- cerning allowable pounds/kilograms per year usage. As expected throughout the industry, the (TLV and Short-term Exposure Limit (STEL) for TCE are being lowered. The American Conference of Governmental Industrial Hygienists (ACGIH), as well as some solvent man- ufacturers, have issued notices of lower values for the above-stated items con- cerning TCE. These new lower values are less than current OSHA guidelines. Earlier this year, in May, the EPA issued its SNAP approval for nPB as a replacement solvent for ozone-depleting chemicals (ODCs) in typical cleaning operations. This approval may now place nPB under future scrutiny by federal, state, and local agencies. One would expect other solvents being used in vapor degreasing to come under similar examination and may be affected in the future. With the existing nPB presence in the degreasing world and recent SNAP approval, will emissive losses and/or workplace exposure limits for users be regulated in the future? Can nPB users expect new OSHA guidelines or local VOC limits or future EPA rules? Today's solvent user would need a very accurate crystal ball to predict any of these. 90

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