Solvent Fire and Explosion

What Happened

A distillation of hexane under inert gas atmosphere was being conducted in a fume cupboard in a research laboratory when a fire and explosion occurred resulting in a student receiving significant thermal burns to his arms, hands, legs, torso and head. He was conveyed by ambulance to hospital and spent 18 days in the burns unit undergoing skin grafting and other treatments. The explosion was clearly heard at a Police Station, over a kilometre away.

Contributing Factors

There were numerous factors, which contributed to the occurrence and severity of the incident, as follows:

1. Procedural Issues

   A tap through which vapour would usually vent from the distillation apparatus was left closed. This meant that the heated vessel of solvent was effectively sealed, and pressure would have built up in the apparatus until part of it gave way, at which time the superheated solvent vapourised.

   The heating mantle used to heat the distillation flask was plugged directly into the mains power outlet, with no power regulation device used. As a consequence, the full heating power of the mantle was applied to the flask of hexane continuously, contributing to the incident.

2. Protective Clothing

   The injured student was wearing shorts, a t-shirt, shoes, socks, and safety glasses at the time of the explosion. Had they been wearing long trousers, a long sleeved shirt and flame retardant laboratory coat, then it is likely that the extent and severity of burns sustained would have been significantly diminished. Their eyes were protected since they were wearing safety glasses at the time.

3. Engineering Controls

   There were purpose built ventilated distillation cabinets available within the department but these were generally used for the distillation of more common solvents.

   The fume cupboards used for this procedure are not free of potential ignition sources. Had this been the case then the hexane vapour would not have ignited and the fire and explosion would not have occurred. It is noted that the fume cupboard light fittings were not spark proof, and that some of the apparatus in the fume cupboard also posed potential ignition sources.

   The fume cupboard did not incorporate a front lip or sump to contain spills, as is now required for fume cupboards under Australian Standards 2243.8-1992.

   A commercial deluge shower is not available in the building concerned. Had a deluge shower been located in the corridor outside the laboratory involved, its prompt use may have reduced the overall severity of the injuries sustained. This also applies to the lack of shower facilities external to the building, where injured persons could be evacuated to during an emergency.

Recommendations

1. Use of Flammable Liquids

   A new flammable liquids protocol is being developed for the use of flammable liquids within the department. This protocol uses a tiered hierarchy of controls and safety measures, which become more stringent with increasing volumes of flammable solvent used.

   Power control devices are to be hard wired to heating mantles, to eliminate the possibility of erroneous omission of them from an experimental apparatus.

   Distillation units are to have signage providing vital information about the procedure and emergency instructions.

   Hazards of ether, petrol and other volatile solvents with low flashpoints and auto ignition temperatures are to be stressed to all personnel.

   That a formal written procedure be developed for all hazardous chemical processes such as the distillation undertaken, and a brief written checklist developed, which can be quickly completed prior to work, to ensure compliance with the procedure.

2. Alternative Procedure

   A feasibility study is conducted of an alterative (less inherently hazardous) solvent purification procedure, which has recently been reported in the scientific literature. If practical to do so then this alternative procedure should be adopted by the department.

3. Clothing

   Protective clothing to be worn at all times in tempered air laboratories will include laboratory coats in addition to the enclosed footwear and safety glasses currently required. When using flammable solvents, the laboratory coat used will be of flame retardant material.

4. Safety Equipment

   Commercial deluge showers and eyewash facilities were recommended for all laboratory corridors and other specific hazard areas within the department.

   Acquisition of self contained breathing apparatus (SCBA) and provision of suitable training in its use was recommended for departmental personnel who may need to deal with chemical spills, and some other situations.

   A number of spare fire extinguishers should be available to facilitate immediate replacement of used extinguishers in high hazard areas. These should be of the same type as those they are used to replace.

   Fixed fire suppression systems be considered for high fire hazard areas in the building.

5. Building

   Fume cupboards to be upgraded to meet current Australian Standards.

   Provision of tempered air is investigated for some laboratories, which become particularly hot during the warmer months of the year. This makes the enforcement of the wearing of suitable protective clothing more practicable and reduces the risk of creating a hazardous situation when handling and storing solvents with lower boiling points.

6. Training

   Whilst the operator had received training in the conduct of solvent distillations, this training had not been formally documented.

   An additional intense week of practical safety training is provided during the first week of third year for all undergraduate students, and to all new research students and personnel to the department.