The Department of Defense told OSHA it planned to adopt new ACGIH occupational exposure guidelines for hexavalent chromium that require different equipment and methodology — measuring inhalable fractions rather than total aerosol concentrations. DoD asked whether the alternative sampling approach could still satisfy OSHA's monitoring requirements.
OSHA said yes. The regulation establishes a performance-based requirement and does not require an employer to use any specific sampling method (29 CFR 1910.1026(d)(5)). What's required is a method of monitoring and analysis that can measure chromium (VI) to within an accuracy of plus or minus 25 percent and can produce accurate measurements to within a statistical confidence level of 95 percent for airborne concentrations at or above the action level of 2.5 µg/m3. Any method meeting those parameters complies.
OSHA also confirmed that employers may use sampling results obtained via an acceptable inhalable fraction method to determine compliance with the OSHA PEL for hexavalent chromium — no conversion to a total-aerosol basis is demanded by the letter.
One limitation: the letter is not approval of an 'alternate standard' for federal agencies under 29 CFR 1960.17, which requires separate Secretary of Labor approval with specific documentation.