CSB Releases Final Investigation Report on 2016 Sunoco Oil Terminal Fire and Explosion in Texas

U.S. Chemical Safety and Hazard Investigation Board (CSB), September 29, 2022

The U.S. Chemical Safety and Hazard Investigation Board (CSB) has released its final investigation report on the 2016 flash fire and explosion at the Sunoco Nederland, Texas crude oil terminal, which resulted in burn injuries to seven workers. In the report, the CSB identified deficiencies in the company’s hot work policies and procedures, as well as the contractors hired to execute the work. The final report highlights key safety lessons learned from the incident at the Sunoco facility, which can prevent future hot work incidents. 

On August 12, 2016, hot work was being conducted by L-Con, a contractor of Sunoco, on a section of pipe that contained residual crude oil. The pipe segment was plugged on both ends by CARBER, a contractor hired by L-CON using an isolation device. During the welding operation on the inside surface of a flange, vapor inside the pipe gathered between two of the installed isolation tools and ignited. The ignition caused a build-up in pressure which led to a violent explosion at either end of the isolated pipe.

Both Sunoco and L-Con developed plans and procedures to provide employees with guidance on how to safely conduct hot work operations, but the CSB found that guidance was inadequate to prevent the fire and explosion. Specifically, the investigation found that the pipe involved in the incident contained residual flammable crude oil which was not adequately cleaned or inerted prior to commencing hot work.  

The CSB concluded that Sunoco’s hot work procedure did not adequately state that hot work on equipment that currently or previously contained flammable material was not permitted by OSHA or NFPA 51B. Additionally, the procedure did not clearly explain how to ensure the equipment was properly cleaned or inerted to safely conduct hot work.  Therefore, Sunoco, and subsequently L-Con, did not implement adequate mitigation strategies to prevent a fire or explosion during hot work activities.

In its final report, the CSB identified three key lessons for industry to prevent a similar incident from occurring. These lessons include:

  1. When isolating equipment in preparation for hot work, ensure the internal atmosphere is not flammable. OSHA’s regulatory requirement and NFPA’s industry guidance both state that hot work shall not occur on equipment that contains flammable material. Cleaning the equipment, purging with inert gas such as nitrogen, or filling the equipment with water prior to conducting hot work are all viable solutions to mitigating the risk of fire and/or explosion.
  2. Thorough identification and assessment of the locations all flammables and combustibles in hot work zones must be completed to develop a robust mitigation plan to prevent fires and explosions. It is important to assess all possible fuel sources (flammable vapors, flammable liquids, combustible materials) when performing hot work to adequately assess the risks and implement sufficient mitigation strategies to prevent incidents.
  3. As stated in the CSB Hot Work Safety Bulletin, released February 2010, seven keys to preventing hot work incidents are using alternative methods to hot work, analyzing and controlling the hazards of the job, conducting effective atmospheric monitoring, testing the general area (even adjacent areas/equipment to hot work) for potential flammable conditions, using written permits that specify the hazards and required precautions, training the workforce thoroughly on hot work policies and procedures, and providing adequate contractor supervision. 



CSB Interim Executive Authority Steve Owens said, “The CSB continues to see hot work incidents at a variety of facilities across the U.S. even though these are well-understood events and are avoidable. Increased adherence by companies to existing regulations and industry guidance can keep other hot work incidents from happening in the future and help protect workers from harm.

The CSB website has additional resources available on safe hot work practices which can be found HERE.

About the CSB

The CSB is an independent, non-regulatory federal agency whose mission is to drive chemical safety change through independent investigations to protect people and the environment. The agency’s board members are appointed by the President and confirmed by the Senate. CSB investigations look into all aspects of chemical incidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems. The CSB does not issue citations or fines but makes safety recommendations to companies, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. For more information, please visit

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