Abstract: On February 7, 1996, Employees #1 and #2 were performing routine maintenance work at Forest Meadows, a private residential development with no industrial or business sites. Employee #1 entered a manhole while Employee #2 stayed on top, watching and handing Employee #1 tools and materials. Prior to entry, the air in the manhole was tested with an Exotox monitor for oxygen, LEL, and hydrogen sulfide. A truck-mounted pressure sprayer was used to clean the interior of the manhole with water to which a small amount of bleach had been added. The estimated concentration of bleach was 27 ppm. No ventilator was used, and the work was completed without incident. No unusual smells or physical symptoms were noted during the work day. At approximately 2:00 a.m. on February 8, 1996, eight or nine hours after finishing work, Employee #1 experienced difficulty breathing and went to a local hospital. He was later diagnosed with bronchial tube damage. On February 13, 1996, Employee #2 sought medical care at Sonora Community Emergency. Both employees received worker's compensation benefits from CAL COMP.