Abstract: An employee working in an etching department entered the work area to remove her material from one of the etching vessels, even though the area was roped off for repair work that she knew was being done on the other vessel. She later indicated that she had entered because the aluminum wafers she was processing had to be removed at that time. One of the gases used in this process was carbon tetrachloride. Normally this was a sealed system, but residual vapors were ambient because the adjacent vessel had been opened for the repairs. Employee #1 inhaled some of the ambient vapors, and 4 hours later reported to the clinic suffering from a headache. She discussed the incident with the company nurse, and was released following an examination. Her headache was gone by the next day. The company safety manager later stated that the employee had been reminded not to enter a roped-off area.