Hazard analysis should consider potential leak locations, potential ignition sources in the vicinity, and the potential for accumulating flammable gases in that area.
Users should leak-check all cylinders upon installation. This event would have been avoided if personnel had followed internal procedures/requirements.
A hydrogen cylinder was initially located in an adjacent laboratory, with tubing going through the wall into the laboratory in use. When the cylinder was moved to the laboratory in use, a required leak check was not performed. Unfortunately, a leak had developed that was sufficient to cause an accumulation of hydrogen to a level above the Lower Flammability Limit. The hydrogen ignited when a computer power plug was pulled from an outlet. The exact configuration of the leak location and the outlet plug is unknown.