Abstract: On April 17, 2006, Employee #1 was welding in a metal shop and was joining mild steel with electric 0.072-inch Innershield NR-232 self-shielded cored wire. The welding process involved DC arc fillet welding, spool-fed flux-core wire, unpainted metal, and no piped-in or external shielding gas. A household fan was used to blow shop air into the welding area. On April 19, 2006, use of the fan was discontinued, and Employee #1 began feeling ill. He saw a number of doctors at SF General Hospital and was initially treated as if he had a common cold. He was later hospitalized for approximately 1 week with brain and heart problems that involved an infection. As of October 2006, the employee was back to work but was not welding.