Abstract: At approximately 10:30 a.m. on August 17, 1990, three contractor employees were removing a blind from an active 36 in. flare header. These employees were wearing supplied air respirators in anticipation of hydrogen sulfide coming out of the line. Four refinery and two other contractor employees were standing by while the blind was being removed. None of these employees was wearing a respirator. When the blind was removed, toxic gas containing hydrogen sulfide came out of the open line. Employees #1 through #4 were standing downwind and were overcome when the gas came out. They were hospitalized.