AB Specialty Silicones, LLC

On the night of 3 May 2019, a catastrophic explosion occurred at the AB Specialty Silicones manufacturing facility in Waukegan, Illinois. The plant specialised in the production of specialty silicone products, including emulsions and raw materials. During a night-shift operation, workers were tasked with preparing a batch of silicone emulsion. The process involved the manual addition of chemical ingredients into a large, open-top mixing tank.

The investigation determined that an operator mistakenly added an incompatible chemical—specifically a reactive polymer containing silicon hydride groups—into a tank that already contained potassium hydroxide (KOH), a strong base. The two chemicals reacted rapidly upon contact, producing significant volumes of flammable hydrogen gas. Because the mixing tank was located within an enclosed production building without adequate ventilation or automated gas detection systems, the hydrogen quickly formed a fog-like vapour cloud that filled the workspace.

Witnesses and survivors reported seeing foam and a "fog" erupting from the tank, prompting a frantic attempt to evacuate. However, within minutes of the release, the hydrogen cloud found an ignition source—likely the facility's non-explosion-proof electrical equipment—and ignited. The resulting blast was powerful enough to destroy the production building and cause extensive structural damage to several neighbouring businesses. Four employees, including a shift supervisor and three operators, were killed in the explosion.

The CSB’s final report, published in late 2021, highlighted critical deficiencies in the company’s "Process Safety Culture." Despite a previous, smaller chemical explosion at the same site in 2014, the company had not implemented a robust hazard analysis program. The investigation found that the drums containing the incompatible chemicals were stored in the same area and lacked clear, distinct labeling to prevent human error. Most significantly, the inquiry pointed to a "regulatory gap" in the United States: the chemicals used at the plant were not specifically listed under OSHA's Process Safety Management (PSM) standard, meaning the facility was not legally required to implement the rigorous safety protocols that might have prevented the disaster. By early 2026, this case remains a cornerstone of the argument for updating international standards to include broader coverage of reactive chemical hazards.