I have written often about this topic and it is without a doubt the most questioned/challenged topic in my 5-Day Advanced Process Safety course. Several toxic substances are listed as regulated substances under 40 CFR ยง68.130 with CONCENTRATION QUALIFIERS (e.g., “conc 37% or greater”). The four(4) regulated substances that have concentration qualifiers are:
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Ammonia (conc 20% or greater)
- Hydrochloric acid (conc 37% or greater)
- Hydrogen fluoride/hydrofluoric acid (conc 50% or greater)
- Nitric acid (conc 80% or greater)
What does this concentration mean?
When determining whether a threshold amount of these substances exists in a process, should I consider the weight of the entire solution, or simply the amount of the regulated toxic substance in the solution?