Abstract: On January 31, 1991, Employee #1, a service/sales technician for Safety Kleen, cleaned a large parts cleaner tank at Winter Chevrolet in Pittsburg with a solvent that was 32 percent methylene chloride. He wore an organic vapor respirator, gloves, glasses, and an apron. He noticed visible vapors emanating from the surface of the liquid in the tank, but did not notice a smell or taste. The odor threshold for this chemical is greater than the PEL. The clean-up job lasted approximately three hours. After he completed this job he proceeded to two other customer sites. His work at these locations did not involve solvent exposure. At 5:00 p.m., he returned to the Oakland Safety Kleen office. When he opened the roll-up door at the rear of his van to unload cans of solvent he felt dizzy and "high." A coworker took him to Merritt Hospital at 5:30 p.m. He was released from the hospital at 7:00 p.m. on February 1, 1991. Employee #1's problems may have been caused by exposure to methylene chloride, although he did not have an elevated carboxyhemoglobin level (a metabolite of methylene chloride).