Occupational Health and Safety Hazard Alert - Explosion in a Materials Engineering Laboratory

This hazard alert is issued following an explosion in a laboratory in Materials Engineering in 1995. Fortunately, the laboratory was unoccupied at the time of the incident and hence no-one was injured.

What Happened?

The cleaners discovered the aftermath of an explosion on 26th July 1995. Safety glass from the door of a storage cabinet was scattered throughout the room, as were numerous broken glass chemical storage containers. Pools of liquid chemicals from these containers were contaminating the floor and other horizontal surfaces. A photograph of part of the laboratory is shown on the other side of this sheet. Occupational Health and Safety was notified and the Fire Brigade informed as required under the Dangerous Goods Regulations. The brigade attended but declined to take part in a clean-up. Due to lack of people trained in Breathing Apparatus (BA) use within the Department, two Occupational Health and Safety staff donned BA and spent the next two days cleaning up. The clean-up was prolonged because of the corrosive and unstable nature of the mixtures of chemicals which had been spilled.

An informal committee of enquiry was held. The committee concluded that the most likely cause of the explosion was either nitric acid/ethanol or perchloric acid/acetic acid - acetic anhydride. Such mixtures are used for metal etching and polishing and were stored in the area. These mixtures are unstable and are known to have caused explosions in University laboratories elsewhere.

Lessons Learned

Although staff and students working in the laboratory had some basic chemical safety knowledge of the materials they were using e.g. corrosivity of acids and flammability of solvents, they did not have a high degree of awareness of additional hazards that might arise with mixtures e.g. instability on storage and formation of explosive by-products. Storage practices were also poor. There was an accumulation of large volumes of old chemicals because there was no disposal procedure in place. Some bottles were unlabelled or had several labels in place so that it was not clear what the current contents were. Chemicals of incompatible classes were stored together rather than being separated by the distances required in the Dangerous Goods Regulations.

The amount of time and effort required to clean-up of what after all, was a small laboratory, proved the importance of emergency preparedness. Having Breathing Apparatus sets available and persons trained in their use is important for reasons such as rescue of someone overcome by fumes and the switching off of gas supply, etc., as well as clean-up. Note that Occupational Health and Safety does not normally have the resources to devote to clean-up following incidents such as this one. Neutralizing agents specific for the chemicals used should be available as part of a "spill kit" e.g. sodium carbonate - slaked lime for areas where hydrofluoric acid is used.

As a result of the committee of enquiry's report, the Materials Engineering department introduced a new chemical's management system whereby all chemicals coming into the department and those mixed up or produced are labelled and colour-coded according to their hazards and limiting the usage/storage time. A mandatory training course on the safe handling and storage of chemicals has been put in place for both staff and students wishing to use chemicals.

Recommendations

Occupational Health and Safety recommends that all departments with laboratories where chemicals are used review existing procedures to ensure that:

1. All containers are labelled clearly.
2. The amounts of chemicals used and stored are minimised
3. Assessment is made of the additional hazards that may arise from mixtures, by-products and intermediates produced during work undertaken in the laboratory. A shelf-life limit for storage and disposal procedure would be part of this assessment.
4. Breathing Apparatus is available for emergency use and that trained staff are available to use it.
5. Special agents are available for neutralizing and cleaning up spills of materials used and produced in the laboratory.
6. Training for both staff and students specific for the special hazards particular to their laboratory environment is provided.

Should you have any further queries please contact Ms. Michelle Wakelam on ext. 51011 or email.

21 February 1996