CSB: Mixture of Incompatible Chemicals Caused Fatal 2019 Explosion

A 15-minute video by the U.S. Chemical Safety and Hazard Investigation Board (CSB) discusses a May 2019 chemical explosion that occurred after two incompatible chemicals were mixed at a Waukegan, Illinois, facility operated by AB Specialty Silicones. The incident caused the deaths of four workers, injured a fifth, destroyed AB Specialty’s facility, and extensively damaged nearby businesses.

The video includes animations demonstrating how, on May 3, 2019, an operator created the first batch of an emulsion product by manually adding and mixing chemical ingredients, including a polymer known as Andisil XL 10, in a tank housed in the facility’s production building. When the operator added potassium hydroxide (KOH) to lower the product’s pH, drums of KOH solution were transported to the area. KOH is highly reactive with XL 10, but the drums containing both chemicals appeared identical. Moreover, the drums of KOH solution were still present when a second-shift operator arrived later to manufacture the next batch of product. The second-shift operator misidentified the drums, unintentionally adding KOH solution to the tank in place of XL 10. As the chemical mixture overflowed the tank, the operator and other workers realized an adverse reaction had occurred but not that the reaction had released flammable hydrogen gas into the production building. Two workers were instructed to vent the building, but before they could do so, the hydrogen gas ignited.

CSB’s video outlines major safety issues that contributed to the incident. Written procedures specifying that incompatible chemicals be stored in different areas and in differently colored drums could have reduced the risk of human error. A building ventilation system design implementing local exhaust ventilation could have reduced the severity of the explosion. The production building did not have a hazardous gas detection system to alert workers to danger, as hydrogen gas is indistinguishable from ordinary air, and the workers had not received effective emergency preparedness training to respond appropriately to adverse chemical reactions.

CSB’s investigation also found that AB Specialty lacked an effective hazard analysis program that could have identified safety issues. In 2014, after a smaller chemical explosion at the facility caused temporary hearing loss to a worker, AB Specialty concluded that a “lack of comprehensive hazard analysis” contributed to the accident, but the company did not make necessary improvements. According to the CSB video narration, “This points to a weak process safety culture at AB Specialty that did not promote effective safety management systems.”

Although AB Specialty used chemicals capable of causing dangerous reactions, the company was not required by existing regulations to implement process safety measures. CSB reiterated a recommendation for OSHA to amend its process safety management standard to achieve more comprehensive control of reactive hazards and require evaluation of reactive hazards. CSB also reissued a recommendation for EPA to revise the accidental release prevention requirements of its risk management plan rule to cover catastrophic reactive hazards that may impact the public.

For more information, read CSB’s news release.