Louisville, Kentucky — A tragic explosion at the Givaudan Sense Colour facility on November 12, 2024, led to the deaths of two workers and serious injuries to three others. The U.S. Chemical Safety and Hazard Investigation Board (CSB) is continuing its investigation into the incident, with a recent update shedding light on the hazardous conditions present during the event.
Following the explosion, which propelled metal fragments over 400 feet, local authorities were compelled to issue a shelter-in-place order affecting a one-mile radius around the facility. The blast not only inflicted injuries but also resulted in damage to nearby homes and businesses, rendering the facility unsafe for continued operations, which have since ceased and are now undergoing demolition.
At the time of the explosion, the plant was in the process of producing caramel food coloring, utilizing a batch reactor. CSB investigators have been analyzing samples from the facility to ascertain whether the reactor experienced a hazardous “runaway” reaction—an uncontrolled buildup of heat and pressure resulting in explosions. The agency’s testing confirmed that conditions were ripe for such a dangerous scenario.
The chemicals involved included sugar, phosphoric acid, sodium hydroxide, water, and an antifoam additive. CSB investigators employed advanced laboratory techniques, such as automatic pressure tracking adiabatic calorimetry (APTAC) and accelerating rate calorimetry (ARC), to evaluate the stability of these materials when subjected to heat in an enclosed environment. These methods involve gradually heating substances in a reaction vessel until a measurable release of heat from a chemical reaction can be detected.
Further tests were conducted to analyze both the batch reactor mixture and the sugar component individually, assessing their contributions to the runaway reaction. Results indicated alarming spikes in both temperature and pressure, surpassing safety thresholds. During tests, pressures exceeded 1,500 pounds per square inch and temperatures climbed above 280°F. The reactions released significant amounts of carbon dioxide gas, which further exacerbated pressure levels.
The CSB noted that this incident reflects a pattern seen in previous accidents it has investigated, highlighting recurrent issues such as batch production processes and rapid, uncontrolled rises in pressure and temperature leading to catastrophic explosions.
As the investigation continues, CSB officials are meticulously examining equipment and the reactor’s safety relief systems to identify the root causes of the incident. The board plans to release a comprehensive final report detailing its findings and recommending safety measures aimed at preventing similar incidents in the future.
The CSB is an independent federal entity tasked with investigating chemical incidents and providing safety recommendations to industry stakeholders, including regulatory agencies like the Environmental Protection Agency and the Occupational Safety and Health Administration. While the board’s findings are critical for industry safety, it does not issue citations or impose penalties for regulatory infractions. Board members, nominated by the president, must be confirmed by the Senate.