Respondent owns and operates a facility that produces, processes, handles, and/or stores a regulated extremely hazardous substance, anhydrous ammonia. The facility uses anhydrous ammonia in a closed-circuit refrigeration system to produce and store ice. Though the ice maker process runs continually, employees are not normally present at the facility outside of business hours. On March 15, 2016, at 22:53, the city Fire Department was notified of a potential release at the facility. Firefighters who responded to the facility believed there had been an anhydrous ammonia release and confirmed that ammonia was in the air by using atmospheric monitoring. The Fire Department notified Respondent's operations manager of the release from the facility. Respondent's employees came to the facility and worked with the Fire Department to stop the release. Following Fire Department protocol, firefighters donned HAZMAT suits to enter the Facility and shut down the compressor. Firefighters remained on site monitoring the air until 05:57 on March 16.