In order to prevent events such as chemical container over-pressurization or catastrophic failure, it is critical to evaluate the full life cycle of chemical management from purchasing, receipt, use and disposal when dealing with time and condition-sensitive chemicals (a chemical that changes characteristics on its own over time and/or depending on storage conditions).
Effects of Incident
Over-pressurization of the container occurred in a tightly controlled waste management area. No one was present during the incident. However, it could have occurred at any time from the 90-day storage area to transport and processing for disposal.
An 800 ml bottle of Borane-tetrahydrofuran complex solution had apparently over-pressurized in a Resource Conservation and Recovery Act (RCRA) Reactive Waste storage room. The over-pressurization caused the glass container to shatter and dislodged one end of an empty metal shelf above the container. There was no evidence of fire, and personnel were not present at the time of the over-pressurization.
Borane-tetrahydrofuran complex solution may form explosive peroxides and is recommended to be stored at 2-8 degrees Celsius (SDS). The bottle was not labeled to require refrigeration but was kept refrigerated by the user. Most likely, this bottle was allowed to warm during transfer from the user to the RCRA storage room. The waste bottle was stored at the RCRA facility at room temperature. Pressure build-up caused the bottle to burst.
Borane-tetrahydrofuran complex solution is also flammable and vapors may form an explosive mixture with air. It also reacts violently with water.
The actual cause(s) of this incident cannot be ascertained with certainty because the rupture of the bottle destroyed any evidence of the exact cause(s). However, there are several possible reasons why this bottle became over-pressurized, with the most likely cause being a temperature increase during storage. Leakage of moist air into the bottle could also have been a cause.
Even if the exact cause was unknown, it was deemed to be prudent to identify actions to prevent the possible causes of this event.
Age of chemical. It is possible the compound can self-decompose with time due to forming explosive peroxides.
Storage temperature. The SDS states: "Recommended storage temperature: 2 - 8° C."
The chemical was handled and stored at room temperature (~20°C). The SDS states: "The pressure in sealed containers can increase under the influence of heat."
Age of septum: Holes in septum may have allowed air into the bottle over time (due to temperature fluctuations of the storage area, air may have infused the bottle due to expansion and contraction).
The techniques of drawing out the material from bottle not performed correctly.
Defective sure-seal cap.
Someone may have tested the cap and broke the seal (Cap was wrapped in Para-film).
Corrective Actions to Prevent Reoccurrence
Label all bottles of Borane THF with a "Keep Refrigerated" label.
Assign an expiration date to peroxide forming compounds, using manufacturers’ recommendations, MSDS, laboratory SME input. Label all bottles with the assigned expiration date.
Communicate with waste generators to provide instructions on how to label temperature sensitive materials that can become unstable or reactive, with a "Keep Refrigerated" label and when determined to be waste, do not place these materials unrefrigerated in satellite accumulation or 90-Day Storage Areas.
Wear proper PPE when handling waste containers including face shield if necessary.
Extent of Condition: Recommended Actions For Time and Condition Sensitive Chemicals
Conduct an Extent of Condition analysis to reveal other classes of chemicals, such as shock sensitive, that also need to be identified and controlled throughout the full life cycle of chemical management from purchasing, receipt, use, and disposal.
The following are additional actions to address this issue.
Develop a list of time and condition sensitive chemicals (e.g., temperature, oxygen, light, water reactive, shock sensitive).
Determine methods to reduce the risks associated with these chemicals including substitution, volume reductions, assigning an expiration date for time and condition sensitive compounds.
Take steps to assure that risks are properly handled throughout the life cycle of chemical management such as:
Incoming chemicals that require refrigeration are kept refrigerated until delivered to the end user.
Label chemicals appropriately, such as using "Keep Refrigerated" or "Expiration Date" labels.
Use overpacks or labpack for time and condition sensitive chemicals directly at the point of waste generation and subsequent transporting to a waste management facility. Chemical is to remain in the lab-pack until disposal.
If needed, maintain refrigerated storage while awaiting offsite transport.
Note: A ’lab pack’ is a hazardous waste disposal term used to describe a container - typically a 55-gallon fiber or steel drum - filled with various small quantity containers of compatible laboratory chemicals. The small containers within the drum are usually packed in vermiculite or other inert packing material to allow safe transport of the waste chemicals.