NOT FOLLOWING PROCEDURES CAN LEAD TO AN INCIDENT

 On September 5, 2023, at approximately 7:30 p.m., an accidental release of butadiene vapor occurred inside a decanting tank (“tank”) at a  facility in Illinois. The butadiene vapors ignited, resulting in a fire that seriously injured one employee.
The incident occurred in the latex production area during a maintenance shutdown. Employees were tasked with removing an internal part (a “baffle”) at the back of the horizontal tank (which was approximately five feet in diameter and nine feet in length). Company procedure stated that the tank should be cleaned using high-pressure water to remove any accumulated solids before entry. However, this procedure was not followed, and residual solids remained in the tank and potentially contained some butadiene. The work inside the tank disturbed these solids, which likely released about two pounds of butadiene vapor, creating a flammable atmosphere within a portion of the tank. In addition, while continual monitoring of the confined space was taking place during the entry, the end of the air monitor hose was not near the bottom of the tank where the solids were located, and this likely prevented the 5-gas detector from identifying the presence of flammable butadiene vapor.

Leading up to the incident, two workers received a confined space permit and a safe work permit to remove the baffle with hand tools after the area was monitored with a gas detector. One of the workers entered the tank (“entrant”) while the other attended the confined space entry (“attendant”). The entrant could not remove the bolts holding the baffle in place with hand tools and switched to a battery-powered
tool, which likely ignited residual butadiene vapors and created a fire. The entrant suffered burn injuries from the fire but was able to escape and was escorted to a safe area by the attendant. The injured worker was transported and admitted to a hospital for medical treatment. Two other employees were able to put out the fire.

Probable Cause
Based on the copmany’s investigation, the CSB determined that the probable cause of the incident was performing work in a confined space containing a flammable atmosphere. Inadequate flammable gas monitoring, the use of a battery-powered tool, and employees’ being unaware that the company had a procedure requiring the tank to be cleaned before entry contributed to the incident.

Source:CSB.gov