Abstract: On August 18, 2008, Employees #1, #2, and #3, the asphalt finisher, dryer-mixer operator, and an operating engineer, started unclogging the asphalt drop chute that fed a 65-ft slat conveyor. The slat conveyor was manufactured by the Gencor Industries, Incorporated and was clogged during the late morning hours. Employees #1, #2, and #3 were spraying diesel on the hardened asphalt and scraping it with a metal scraper. At approximately 11:45 a.m. the drop chute was cleared. By the time the second batch of asphalt mixer was deposited into the drop chute, Employees #1, #2, and #3 heard a loud explosion and the plywood panels, along with their metal straps, were blown off and scattered around the plant yard. Employees #1, #2, #3, and a plant supervisor complained about ringing in their ears and hearing problem due to the blast. The following day, Employees #1, #2, #3, and the plant supervisor went to San Francisco General Hospital for hearing tests. The preliminary tests showed that Employees #1, #2, #3 experienced changes in their hearing thresholds. They were recommended to see a specialist. The suspected cause of the explosion was presence of a source of ignition of an unknown origin in a flammable atmosphere, created by the vaporized heated diesel. The manufacturer's manual warns against using combustible release agent. However, employer was using diesel, Fl.Pt.146 F, as the release agent and a cleanup fluid because of its effectiveness.