A glass bottle containing chemical waste exploded due to a reaction caused by incompatible chemicals being placed in the container. No injury resulted from the incident; however, impacts were significant. This type of incident can be prevented by controls that are available to all labs.
APPLICABLE SAFETY PRINCIPLE
Proper chemical storage (chemical wastes or materials used in protocol) involves specific controls to be carried out by the lab. These controls include the use of chemical segregation guidelines, standard operating procedures, engineering controls, and inspections of the areas to ensure compatible storage
A lab staff person working approximately 8 meters from a chemical fume hood heard a "hissing" sound emanating from this hood. Approximately 10 seconds later, a loud explosion erupted and material shot out of a storage area with enough force to blow a cabinet door off of its hinges and cover a substantial portion of the lab with glass, a cabinet door, and a copper-colored liquid. Approximately 15 minutes prior to this explosion, safety representatives were en route to this location to collect chemical waste. Had a delay not occurred, these representatives may have been in the immediate vicinity of the explosion.
The reaction was caused by incompatible materials added to the same waste container. It is believed that nitric acid was added to a brown glass bottle that previously held an organic material. As the gas built up, the pressure in the container increased until the glass reached its breaking point.
RESPONSE AND CORRECTIVE ACTIONS
Immediately after the explosion, lab staff contacted safety personnel who reported to the scene and inspected the incident area, along with lab staff and subject matter experts. Investigators were joined by University Police who obtained information on location, occurrence and involved personnel.
Immediately adjacent to this area was a "Weekly Container Integrity Inspection" sheet that had been checked off and initialed for each week, most recently being four days prior to the incident. Despite this, lab staff could not initially determine the contents of the bottles shattered by the explosion. After observing the copper-colored liquid found in the vicinity, colorimetric change from potassium iodide starch paper for detection of oxidizing agents, and additional questions answered by lab staff, it was concluded that nitric acid was in one of the shattered bottles. The brown bits of glass, including a piece of a circular handle, indicated that a four-liter waste bottle containing organic material was stored in the particular area of explosion.
The lab was shut down immediately for two days to clean up the area, discuss root cause and contributing factors, and receive special safety training. While all lab personnel were restricted from the immediate area, the area was safely cleaned and decontaminated.
CAUSE ANALYSIS AND PREVENTATIVE MEASURES
As illustrated in the figure below, the following factors contributed to the incident:
- The lack of knowledge regarding the components of the chemical waste storage area clearly revealed that routine (weekly) hazardous waste area inspections were lacking. Moreover, acids were collected in an area restricted for flammable materials.
- A lack of procedural bases for handling mineral acids existed in the lab. Safety offices provide guidance on development of SOPs; but must rely on labs to provide specificity on protocols and to make the SOP pertinent to specific lab operations. This did not exist.
- Engineering controls, including the use of vented caps were not being utilized. These vented caps are intended to prevent pressure build-ups that may occur in containers.
Training was lacking. Though safety training is provided to labs, the importance of engineering and administrative controls (e.g., signage and guidance) was not fully understood. One example is the Basic Chemical Segregation Guideline, which enables labs to safely organize chemicals.
There are means at Georgetown for preventing these types of incidents.
1. Lab staff are required to review and follow the hazardous waste inspection procedures. Follow this link to review the Chemical Waste Safety Module
2. Procedures must be developed and shared to enable effective controls for highly hazardous materials and situations. Standard Operating Procedures are required for many toxic and physically hazardous substances. When working with the safety offices, labs should include adequate control measures (e.g., special handling procedures, vented caps) in these procedures.
3. All researchers should prioritize the use of hazardous chemicals, as well as physical hazards, in order for the most dangerous conditions to be fully addressed. Training must emphasize previous lessons learned (examples pertinent to waste segregation and chemical compatibility), which can be used to preclude incidents resulting from incompatibility.
4. Proper segregation of chemicals may be found in the laboratory Chemical Hygiene Plan or the Basic Chemical Segregation Guidelines.