Formic Acid Explosion

What happened

An explosion involving formic acid occurred within the storage compartment underneath a fume cupboard in a University of Western Australia (UWA) undergraduate laboratory. The force of the explosion blew out the plastic panelling of the storage compartment and extensively damaged the sink and plumbing in the fume cupboard. All but three of the nine glass winchesters of chemicals in the storage compartment were broken and glass, chemicals and plastic debris forcefully blown throughout the laboratory. The explosion occurred at 7.40 pm on a weeknight and fortunately no one was injured.

Cause of the explosion

The most likely cause of the explosion was a build up of pressure in a formic acid winchester. Formic acid (HCO₂H) slowly decomposes with the liberation of carbon monoxide. A 2.5 litre bottle of 98-100% formic acid solution in the absence of a gas leak would be expected to develop a pressure of 7 atmospheres during 1 year at 25^oC. Whilst manufacturers have been using pressure relieving caps for many years it may be possible to seal these bottles with non venting caps, or for older stock to be held which does not have this venting facility.

It should be noted that whilst some manufacturers material safety data sheets (msds) clearly state that 98-100% formic acid should be "stored in vented containers to permit release of internal pressure", some msds stated that the chemical should be "kept in a tightly closed container".

Recommendations

If old stocks of formic acid are held which does not have a venting cap and which has not been opened recently, it is recommended that expert advice and assistance be sought to safely vent these containers. It is noted that a storeman at the University of Sydney lost an eye  when a bottle of formic acid exploded as he lifted it off a shelf. All containers of formic acid should have vented caps or be safely vented on a regular basis.

For information on formic acid and other potentially explosive laboratory chemicals see the Australian National University (ANU) hazard alert at the following address: http://info.anu.edu.au/HR/OHS/Hazard_Alerts/_Formic_Acid_Explosion.asp

Follow up actions at UWA

A thorough chemical safety audit was conducted of the UWA department following the incident. The major changes introduced were improvements to the chemical management systems within the department including

• Written policies and procedures, including safety booklet
• Safety awareness information, instruction and training of staff and students
• Physical workplace improvements, including equipment and signage
• Supply, handling, storage and disposal of chemicals
• Regular inspections of workplaces and work procedures
• Emergency planning and response procedures

Some of the specific recommendations made following the thorough chemical safety audit of the department were:

• up to date register of all hazardous substances and dangerous goods required
• ensure segregation of dangerous goods within all areas
• dispose of all old or unwanted chemical stocks regularly
• secure all gas cylinders individually with brackets and chains
• ensure all laboratory refrigerators are made spark proof and labelled
• ventilation bungs be replaced in cabinets not mechanically vented
• Class 3 (Flammable liquids): stored in proper storage cabinets mechanically vented
• 4.2 (Spontaneously combustible) and 4.3 (Dangerous when wet): used over metal or other fire resistant bunding trays
• 4.2 (Spontaneously combustible) and 4.3 (Dangerous when wet): buckets of clean dry sand be available for use in case of spillage or fire
• 5.1 (Oxidising agents): not be stored directly on wooden or other combustible shelves
• 5.2 (Organic peroxides): stored in plastic bunding trays, check of dried out containers
• 6.1 (Poisons/toxic): cyanide removal or compliance with regulations
• 6.1 (Poisons/toxic): storage in locked poisons cabinets
• 8 (Corrosives): segregation into groups, regular checking of bunded containers
• unstable chemicals: removal, checking, use
• chemical spill kits made available
• register be made available and kept up to date for after hours contact
• emergency information package prepared
• use of personal protection equipment, including closed shoes, eyewear
• cleaning out procedures:  annual, completion of studies, departures
• written guidelines, procedures and instructions for storage and use of chemicals
• establishment of a Departmental Safety Committee
• regular safety inspection of department
• improved signposting
• regular checking of plastic squeeze type eyewash bottles
• location and ducting of fume cupboards
• provision of fire blankets and training in use of these and fire extinguishers
• mandatory use of safety carriers for transporting winchesters