Frequent Questions

Threshold calculations for acid mixtures

Do you apply the whole weight of an acid mixture towards the threshold under EPCRA Sections 311 and 312 or just the percentage of acid stated on the material safety data sheet (MSDS)?

Aqueous acids are considered mixtures under EPCRA Sections 311 and 312.  The acid itself is the hazardous chemical mixed with water when in solution.  If the MSDS for a hazardous chemical which is not an EHS provides percent concentration information, the facility may use the percentage of acid stated to determine if thresholds have been met for that component.  If no information is given, or if the facility is applying the threshold to the mixture as a whole, it must apply the entire amount of the mixture towards the threshold.  For acids which are extremely hazardous substances (e.g., sulfuric acid), the facility must determine if the thresholds have been met for that component.

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