Abstract: On June 12, 2007, Employees #1 and #2 were installing a shim (test probe) into a heat furnace. This function requires two people, where one worker inserts the shim into the furnace, while the other worker simultaneously opens the door of the furnace, by means of a remote foot pedal, to prevent hot gases under pressure from jetting out of the shim port when the valve is opened for insertion of the shim. While Employee #1 had the furnace valve opened and was inserting the shim, Employee #2 depressed the foot pedal, which was located approximately 15 feet from the furnace. At this moment, an electrical cabinet next to the shim port blew out. Employee #1 was knocked backwards by the door of the cabinet and received a penetrating chest wound, and lacerations to his head, face, arms, and upper body from the flying debris. Employee #2 was blown back several feet as well from the explosion, suffering a few minor bruises. Employee #1 was taken to a nearby hospital, where he was hospitalized and underwent surgery. The incident investigation showed that a pump used to sample the gases in the furnace during heat treating had been placed in the electrical cabinet. The pump was rated only to pump air and to operate at temperatures below 104 degrees Fahrenheit, but the gases that were sampled from the furnace were normally several hundred degrees. The mixture also contained an organic chemical. The combination of high temperatures and the presence of the organic chemical were determined to be the route cause, resulting in failure of the pump seals and o-rings. This failure then allowed the gas mixture to seep into the cabinet, accumulate, and ignite when the relay to open the door of the furnace was tripped resulting in the explosion.