An independent federal agency that investigates major chemical incidents released an update June 18 to its ongoing investigation into the Givaudan Sense Colour explosion that struck Louisville’s Clifton neighborhood in November 2024, finding that the chemicals involved are capable of causing a “hazardous runaway reaction.”
The five-page report from the U.S. Chemical Safety and Hazard Investigation Board describes chemical testing of the caramel coloring ingredients used the day of the explosion and illuminates how a rapid and uncontrolled rise in temperature and pressure inside a pressure vessel may have contributed to the explosion that killed two workers and injured several others at the plant.
Investigators performed two types of laboratory tests, which entailed incrementally heating the materials in a reaction vessel until the materials increased in temperature without intervention, according to the report. The tests were designed to evaluate the stability of the chemicals when heated in an enclosed vessel.
Temperature increased significantly and gas was produced during the reactions, contributing to spikes in temperature and pressure well beyond the vessel’s limits for safe operation, according to the report.
The U.S. Chemical Safety and Hazard Investigation Board is continuing its investigation with additional chemical testing, analyzation of equipment recovered from the explosion site and evaluation of the vessel’s pressure relief system.
In an update released by the board in February, investigators shared that pressure and temperature inside the vessel far exceeded the limits for its safe operation the day it exploded. Investigators also determined the vent valve — a mechanism meant to regulate the vessel’s pressure — was “almost fully closed.”
The temperature in the vessel rose to as high as 385 degrees the day of the explosion — 30 degrees higher than its maximum of 355 degrees — and the pressure rose to 237 psig — more than three times its maximum, according to the February report.
The latest report comes on the heels of a Kentucky Occupational Safety and Health Program investigation that resulted in $21,000 in fines and four serious safety violations for Givaudan, The Courier Journal reported.
One of several findings mentioned in the state report was that the exploding vessel had prior issues with overpressurizing. A work order from September 2023 cited in the report noted one instance when the vessel overpressurized because the control room screen indicated its vent valve was fully open when it was actually only 5% open.
The same “false communication” between the control room and the vent valve’s physical position occurred prior to the November explosion, according to the report.
Givaudan officials have said they do not plan to rebuild on the site, though they have not identified where they will move. Mayor Craig Greenberg announced in April that local officials are working with the company on a plan to demolish the plant in summer 2025.
More: State investigation into Givaudan finds safety violations, prior vessel overpressurization
Contact reporter Killian Baarlaer at kbaarlaer@gannett.com or @bkillian72 on X.
This article originally appeared on Louisville Courier Journal: US Chemical Safety Hazard Investigation Board on Givaudan explosion