Explosion in an academic laboratory

The explosion was caused by the ignition of hydrogen during reaction with sodium metal.

The Chemistry Department routinely dried solvents using metallic sodium. This leaves an excess of sodium metal, which need to be disposed. This is done by oxidising it by a reaction with a toluene solution of isopropyl alcohol (IPA), prior to disposal.
The by-products of this reaction are hydrogen gas and heat.
The operation was performed by a PhD student, who had already executed it before. He left the reaction for approximately four hours in the fume cupboard. Upon return, he added more IPA to complete reaction. The production of hydrogen and heat accelerated. The hydrogen ignited and exploded, and the solvent ignited and ejected out of fume cupboard onto him.
He was lightly injured.

The INITIATING CAUSE was an excessive production of gaseous hydrogen during a reduction reaction.
The reaction between metallic sodium and a alcohol oxidises sodium and produces gaseous hydrogen. it is a exothermic reaction and therefore produces also heat. The quantities used are unknown, as well as the temperature reached by the reaction. Also the CAUSE of the ignition is unknown, but it is clear that the quantity of hydrogen produced was enough to produce an explosion.
The root CAUSE was probably the lack of a correct risk assessment. According to the event source (HSE, see references), the department had performed a risk assessment for individual substances but not for the reaction.

Process to oxidise metallic sodium metal. fume cupboard.

The chemical reaction operation was performed in a fume cupboard. The reason of the ignition is unknown, as well as the temperature reached by the reaction.

DESCRIPTION OF THE FACILITY
It implies the oxidation of metallic sodium (Na) by reacting it with an alcohol, to produce sodium hydroxide (NaOH). In the case of the accident, a solution of isopropyl alcohol (C3H8O) was used, in solution in toluene (C7H8) which is chemically inert.

The PhD student burnt right hand & right side of face, which healed quickly.

The university department planned to buy anhydrous solvents, to reduce excess sodium metal production. They investigated as well safer methods to destroy metallic sodium.