Ammonium hydroxide is a solution of ammonia in water. If a facility stores ammonium hydroxide (CAS #1336-21-6) in a large storage tank on site, should the facility include the quantity of ammonia in ammonium hydroxide for section 302 emergency planning notification?

The emergency planning notification requirement in section 302 applies to facilities that have extremely hazardous substances (EHSs) equal to or in excess of their threshold planning quantity (TPQ) at any one time. Ammonia (CAS #7664-41-7) and ammonium hydroxide (CAS #1336-21-6) are considered different chemicals for purposes of EPCRA section 302 notifications. Notifications under EPCRA section 302 are required for ammonia as it is a listed Extremely Hazardous Substance (EHS) (40 CFR part 355 Appendices A and B), with a TPQ of 500 pounds. Ammonium hydroxide is not an EHS and therefore no notification is required under EPCRA section 302, however, a facility storing a large quantity of ammonium hydroxide may have free ammonia in the headspace of the storage tank. The facility must notify under EPCRA section 302 if the ammonia in the headspace of the storage tank equals or exceeds its TPQ of 500 lbs at any one time.