On Aug. 28, 2016, an Airgas employee began the process of transferring nitrous oxide, also known as laughing gas, into a trailer. A pump being used in the operation heated the gas above its safe operating limit, triggering the nitrous oxide to rapidly decompose in the pump.
The reaction then moved from the pump into the trailer and caused an explosion which killed the Airgas operator, scattered large metal fragments for hundreds of feet.
The facility also was badly damaged, and Airgas had to stop production of nitrous oxide indefinitely.
The Chemical Safety Board (CSB) began an investigation into the incident. It discovered that while some federal regulations require some chemical facilities that manufacture hazardous substances to have process safety management systems in place to protect their workforce and the public, these same rules are not required for facilities that make nitrous oxide.
“Nitrous oxide is a hazardous substance – facilities should have good safety management systems to mitigate the risks that exist,” Vanessa Allen Sutherland, CSB Chairperson, said in a statement. “Safety management systems standards are critical to identify, evaluate, and control process safety hazards. This tragedy in Cantonment should not be repeated.”
The CSB stated the contributing causes of the explosion directly were correlated to the lack of an effective process safety management system.
Most notably, Airgas did not evaluate safer design options that would have eliminated the pump, which was a known hazard. The company also did not perform a management of change review or hazard analysis before installing the pump.
Lastly, the safety interlock which was installed to automatically shut down the pump as well as the flame arrestors did not adequately protect employees from the heat hazard, and therefore failed to prevent the explosion.
“We looked at other possible causes such as static electricity, but the available evidence, it appears that the bypass of the safety interlock on the pump during startup likely allowed the pump to overheat and trigger a decomposition reaction,” Lead Investigator Dan Tillema said.
Because of the lack of regulatory procedures and safety processes, the CSB recommended the following to Airgas as well as the Compressed Gas Association and two other nitrous oxide manufacturers: the development and implementation of a safety management system standard for nitrous oxide manufacturing and the distribution of increased warnings about nitrous oxide decomposition hazards.
Our recommendations reiterate the importance of safety management systems as critical to control hazards during the manufacturing, transferring, and shipping of nitrous oxide,” Sutherland said. “Strong safety management systems are good business practices, which also save lives.”