Abstract: Employees #1 through #16 were making a variety of ice cream and ice cream novelties. The temperature in the mixing and storage area is kept at about 35 degrees by an ammonia evaporator unit. The unit consists of a left-hand unit and a right-hand unit. The right-hand unit, model #LCB-45-0408-AA-056-717R, serial #92-R-1745-A, was in defrost mode and was operating at about 90 psig when the system malfunctioned and the weld around the 3 in. diameter metal cap of the suction header failed. The cap was blown from the evaporator and ammonia leaked from the evaporator unit for about 5 minutes until the valve to the feed line was manually shut off. The ammonia alarm sounded and the facility was evacuated. The employer has a trained hazardous materials response team that responded with the appropriate equipment and cleared the facility with the help of the local fire department. Eighteen employees experienced minor injuries such as eye, nose, and throat irritation, headaches, and nausea. Employees #1 through #16 were transported to the hospital, treated, and released.