CSB final report on Givaudan Louisville explosion: runaway reaction, undersized relief, and a control room 40 feet away

The U.S. Chemical Safety Board has released its final investigation report on the November 12, 2024 explosion at the Givaudan Sense Colour caramel-coloring facility in Louisville, Kentucky, which killed two workers, seriously injured three others, and caused roughly $40 million in damage to the plant and surrounding community.

What happened

A 2,500-gallon reactor producing caramel coloring experienced a runaway decomposition reaction involving the sugar ingredient in the process. The pressure rise overwhelmed the reactor’s emergency pressure relief system and the vessel ruptured violently. The CSB found the relief system would have needed to be approximately four times larger to safely relieve the pressure generated by the runaway.

The reactor shell — about 2,000 pounds — was thrown 245 feet into a residential neighborhood. Debris traveled up to 400 feet beyond the fence line. The two fatalities occurred in a control room located just 40 feet from the reactor: it was not blast-resistant, and the blast wave collapsed it onto the workers inside.

The vessel itself had a history worth noting. Built in 1978 for a different facility, it was kept in storage after that site closed in 2008, then modified and installed at Louisville in 2021.

Findings

The CSB concluded that the company did not understand the severe reactive hazards of the sugar ingredients used in the process, and as a result the safeguards in place — including the emergency relief system — were incapable of preventing a catastrophic rupture. CSB Chairperson Steve Owens called the incident “a catastrophe waiting to happen.”

The report’s recommendations fall into three groups. To Givaudan, it recommends third-party reactivity testing of sugar ingredients, facility hazard analyses, comprehensive process safety management systems, improved emergency relief design, operator alerts, and training on safe operating limits. To regulators, it reiterates long-standing recommendations that EPA revise its Accidental Release Prevention Requirements to explicitly address reactive hazards, and that OSHA expand the PSM standard to do the same. On siting, it emphasizes that companies should analyze normally occupied buildings — control rooms especially — against identified process hazards and redesign where needed.

Lessons for hazard studies

Three threads stand out for practitioners. First, reactive hazards in “benign” chemistry: a food-ingredient process using sugar produced a runaway decomposition that the operator’s hazard identification never captured. Second, relief-system basis of design: relief sizing is only as good as the design-case reaction it assumes, and a hazard study that does not interrogate the relief basis against credible runaway scenarios leaves the last layer of protection unverified. Third, relocated and repurposed equipment: a vessel moved between facilities and modified decades after construction needs its design basis re-established, not carried over.

The full report is available on the CSB investigation page.