Abstract: At approximately 7:45 a.m. on Friday, September 17, a maintenance employee mixed a chlorinating agent (containing 65 percent chlorine) with a stabilizer agent (containing isocyanuric acid) and added it to the filter basket of a water circulating system that served the pools and decorative fountains of an office complex. The system was located in a small pump room (14 ft by 24 ft) in the basement of the building. The incorrectly mixed chemicals began to bubble out onto the floor through a damaged O-ring around the top cover of the filter basket. Another maintenance employee twice tried to enter the room to neutralize the mixture with soda ash, but could not. All SCBAs were unavailable because they had been sent out for servicing. The area was evacuated and the fire department and EMS were called in to clean up. Employees #1 through #5 were checked at the hospital and released. The employees had not been trained properly.