Abstract: At approximately 1:50 a.m. on July 10. 1988 Employee #1, a refrigeration operator employed by Coldwater Seafood Corporation, began to change the oil of a Frick #9 compressor unit of an ammonia system. After closing the condenser valves, he changed the oil in the compressor unit, and then decided to clean the sight glasses of a booster compressor. He removed the screws which held the glass in place and as soon as he had backed these screws out far enough, pressure in the system blew the glass plate off and a surge of ammonia contacted his face causing him to inhale ammonia. Pressure was present due to the fact that sometime after having changed the oil he had reopened the discharge valve. He does not recall reopening this valve, but he had since he was alone and this valve was open when the fire department arrived. After the dose of ammonia, Employee #1 tried to put on respiratory protection equipment but could not because his glasses had been knocked off and he could not see. He did secure the condenser valves on the roof and was then taken to the hospital for treatment.