Must a stationary source owner or operator consider the amount of ammonia present in ammonium hydroxide that is contained in a process when determining whether the threshold for ammonia is exceeded?
The list of regulated toxic substances at 40 CFR Section 68.130 includes BOTH
“ammonia (anhydrous)” and
“ammonia (conc 20% or greater)”
but does not include a specific listing for “ammonium hydroxide.” The Chemical Abstract Registry Service (CAS) number for ammonium hydroxide is 1336-21-6, and the CAS number for ammonia is 7664-41-7. Ammonium hydroxide is, however, simply a mixture of ammonia and water.
YES – a stationary source owner or operator MUST consider the amount of ammonia present in ammonium hydroxide that is contained in a process when determining whether the threshold for ammonia is exceeded.
For the purposes of the risk management program regulations at 40 CFR Part 68, ammonium hydroxide must be treated as a solution of ammonia and water, regardless of the fact that ammonium hydroxide may be identified by a unique CAS number.
The Agency has made it clear that the listing for “ammonia (conc 20% or greater)” applies to aqueous solutions of ammonia (List Rule Response to Comments document, page 50).
If the concentration of ammonia in the ammonium hydroxide is 20% or greater, then the mixture is subject to threshold determination for “ammonia (conc 20% or greater)” under 40 CFR Section 68.115.
Source: https://www.epa.gov/rmp/ammonia-present-ammonium-hydroxide