At 11:30 a.m. on September 04, 2018, a group of employees was working on a beef processing station. Employee #1 was REPLACING A DEFECTIVE AMMONIA PRESSURE GAUGE FOR A HOT-GAS AMMONIA LINE when he broke off the gauge and associated valve, releasing ammonia into the area and cut/fab floor below. The plant was evacuated and 14 employees were treated and released for ammonia exposure and one employee was hospitalized overnight. It was calculated that approximately 61 LBS. OF AMMONIA LEAKED DURING A 22 MINUTE PERIOD.