Abstract: Employees #1, #2 and #3 were working in Department 501. Employees #1 and #2 were cleaning the ion deionizer. The deionizer is an approximately 100 gallon composite tank housing an ion exchange resin. The top valve on the tank was removed and the resin was being recharged. One employee added ten gallons of sodium hypochlorite to the ion exchange resin. He then stuck a metal wand approximately seven feet long into the bottom of the tank. The employee used the compressed air wand (approximately 85 psi) to stir up the resin. When the compressed air was shot into the tank, the material in the tank spouted out of the top and the employees were exposed to acidic vapors. They suffered from extreme coughing, burning sensations, chest tightness, and other related symptoms. Employees #1 through #3 were sent to the hospital and received oxygen. Employee #1 was kept overnight for observation.