Respondent produces meat and protein products for sale by third-party customers. As part of this process, Respondent uses anhydrous ammonia in a chill tank to prepare and preserve the products. Ammonia is a regulated substance listed in Table 1 to 40 CFR § 68.130. On the evening of January 15, 2016, after the Facility had closed its operations, a worker employed by a sanitizing equipment was sanitizing a chill tank in the Chill Tank Room within the Cooked Food Department (a.k.a., the Ready-to-Eat or “RTE” Department). The sanitation contract worker was the only person in the Chill Tank Room. The chill tank has a drain valve that can be manually opened or closed by turning its handle several times counterclockwise or clockwise (a.k.a. Oil Drain Valve). The sanitation contract worker did not have authority to open the Oil Drain Valve and had not been instructed to do so. Although Worker denies opening the Oil Drain Valve, no one else had access to the Chill Tank Room at the time. It is believed that the sanitation contract worker mistakenly opened the Oil Drain Valve. When the valve was opened, ammonia was released at approximately 9:30 p.m.