Forty-six hydrogen cylinders were accidentally charged with air instead of additional hydrogen during recharging operations at a synthetic liquid fuels laboratory. Cylinders were manifolded in batches of 10 or 12 to the utility compressor outside the laboratory. In normal operations, partly used cylinders containing hydrogen at a pressure of 800-900 psi were recharged to a pressure of 2000-2100 psi. Since the contaminated cylinders contained a highly explosive mixture of about 40% hydrogen and 60% air, it was decided to release the compressed gas to the atmosphere outside the building after grounding the cylinders. Two of the cylinders were successfully discharged, but an explosion occurred while the third cylinder was being discharged. Two chemical engineers were killed by the blast, an operator was injured and required hospitalization, and the laboratory building and equipment were damaged.

The investigating committee postulated that 1) there may have been oil present in the regulator that ignited at a relatively low temperature and then ignited the hydrogen-air mixture, or 2) there may have been a metallic compound present that catalyzed the oxidation and subsequent ignition of the hydrogen-air mixture. Other possible causes that were considered less likely were 1) the existence of a leak around the attachment of the regulator to the cylinder, with ignition of the leaking gas by friction or static spark, and 2) ignition of the cylinder contents as a result of the electrical potential of a fire alarm post against which the cylinder was leaning while being discharged.

The probable cause for the contamination of the hydrogen cylinders was that the 3-inch gate valve on the hydrogen intake line to the compressor was closed during the filling operation. It was not possible to determine with certainty how the air entered the system due to conflicting testimony of laboratory employees. However, it likely entered through one or more of the many valves on the compressor suction system, any one of which may have been inadvertently left open.