Abstract: During the afternoon of January 21, 2005, four employees were working in a room containing equipment that was designed to use an electro-coagulation system to remove arsenic from process water. Adjustments to the system were being implemented to increase the speed of arsenic coagulation. By the following morning all four workers were passing urine which was blood red in color, and all four had been admitted into hospitals. The inhalation of Arsine gas caused the symptoms and adverse medical consequences which have been exhibited by these four employees. Excessive levels of Arsenic have been found in their systems. The leading theory concerning the mechanism of generation of Arsine gas was that nascent hydrogen could form when an electric current flowed through an aqueous solution containing substantial concentrations of electrolytes. This hydrogen could react with the arsenic present in this solution to form arsine gas. The workers who suffered the most severe medical consequences spent prolonged periods of time on an elevated platform, looking directly down into the Electro-Coagulation Unit, and making observations as various adjustments were made to the process, such as changes in the amperage of electric current flowing through the process liquid which contained dissolved compounds of arsenic. The use of sulfuric acid to periodically clean the unit and the iron plates which it contained might also have been a contributing factor. Two of the four hospitalized workers displayed little or no functioning of the kidneys and underwent dialysis.