Abstract: On July 2, 2008, three employees were performing maintenance and repairs on a four-bottle oxygen cart, a piece of ground-based equipment used to support aircraft oxygen systems. Employees fabricated and assembled four pigtail hoses that connected the cart's "K" size aviator oxygen cylinders to an aluminum manifold. Following reassembly, the employees were checking the system for leaks, opening one cylinder valve at a time pressurizing the pigtail hose, the manifold, the downstream regulator, and outlet hose. Seconds after one of the cylinder valves was opened, an ignition occurred within the manifold which then failed, and a violent flash fire ensued in the oxygen enriched atmosphere during the cylinder's uncontrolled discharge. The three employees exposed to the fire were hospitalized with second and third degree burns.