Recently OSHA rescinded all their previous LOIs regarding how to calculate your HHC in your process when it is NOT in pure form. Since then I have fielded dozens of phone calls and countless emails asking questions about OSHA’s change and how it impacts their process. OSHA’s new enforcement policy is as follows:
In determining whether a process involves a chemical (whether pure or in a mixture) at or above the specified threshold quantities listed in Appendix A, the employer shall calculate:
(a) the total weight of any chemical in the process at a concentration that meets or exceeds the concentration listed for that chemical in Appendix A, and
(b) 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 one percent or greater. However, 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 (mm Hg). The employer shall document this partial pressure determination.
So how does this apply in real-life?