Abstract: On April 22, 2002, Employees #1 through #3 were in a 3-ft-deep excavated area in the basement of a three-story multi-family residence, performing a seismic retrofit of the structure. Employee #1 was spraying diesel fuel on a concrete surface prior to the application of wood form work to prevent the formwork from adhering to the existing concrete. Employee #2 was using a Craftsman rechargeable drill to install screws onto a piece of wood formwork, and Employee #3 was holding an electric lamp to illuminate the work area for Employee #1. The drill evidently ignited the atomized diesel fuel vapor. Employees #1 and #2 suffered second-degree burns to both forearms, both hands and their faces. Employee #3 suffered second-degree burns to his face. All three employees were hospitalized at Alta Bates Medical Center.