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OSHA Changes Policy on Concentration of Chemicals

Tuesday, August 18, 2015

OSHA has revised the enforcement policy on the concentration of a chemical that must be present in a process for the purpose of determining whether the chemical is at or above the threshold quantity listed in Appendix A of the Process Safety Management of Highly Hazardous Chemicals (PSM). OSHA’s previous policy was found to be potentially unsafe for use around hazardous chemicals.

Under OSHA’s revised policy, an employer is required to use a new process to calculate the following:

  • The total weight of any chemical in the process at a concentration that is at or above the concentration listed for that chemical in Appendix A
  • With respect to chemicals for which no concentration is specified in Appendix A, the total weight of the chemical in the process at a concentration of 1 percent or greater.

The employer need not include the weight of such chemicals in any portion of the process in which the partial pressure of the chemical in the vapor space under handling or storage conditions is less than 10 millimeters of mercury. The employer must document this partial pressure determination.

For more detailed information, refer to the full policy changes at


Material posted on this website is for informational purposes only and does not constitute a legal opinion or medical advice. Contact your legal representative or medical professional for information specific to your legal or medical needs.

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