A facility has 9,000 pounds of ammonium hydroxide (19 percent solution) present on site at a given time. For reporting under EPCRA section 312, must the amount of ammonia in ammonium hydroxide be counted (and aggregated) towards the reporting threshold for EHS? 

Under EPCRA section 312, the reporting threshold for Extremely Hazardous Substances (EHS) is 500 lbs or the threshold planning quantity (TPQ), whichever is less. (Note: The TPQ for ammonia is 500 lbs). Except for gasoline and diesel fuel, all other hazardous chemicals, including ammonium hydroxide, have a reporting threshold under EPCRA section 312 of 10,000 lbs. Ammonia (CAS number 7664-41-7) is an EHS (40 CFR part 355, Appendices A and B).  Ammonium Hydroxide is made by combining ammonia and water. However, ammonium hydroxide has its own distinct CAS # (CAS number 1336-21-6) and is not listed as an EHS.  The facility would only be required to report if the amount of ammonium hydroxide exceeds the EPCRA section 312 threshold of 10,000 lbs. However, if free ammonia exists in the headspace of the storage tank, the facility must determine whether the amount of ammonia exceeds the EPCRA section 312 EHS reporting threshold of 500 lbs, and if so report that amount on their Tier II form.