June 20, 2024

CSB Outlines Initial Findings in Investigation of 2023 Ethylene Oxide Release

The U.S. Chemical Safety and Hazard Investigation Board (CSB) is examining reactive chemical hazards and emergency pressure-relief systems as part of its investigation of an explosion that resulted in the release of more than 31,000 pounds of ethylene oxide (EtO) at a Dow plant in Louisiana last year. The facility is an industrial park comprising 23 production units where more than 50 intermediate and specialty chemical products, including EtO, are manufactured. Events that led to the release on July 14, 2023, include high vibration in a reflux pump, upsets to the EtO finishing process, and multiple explosions and fires, according to CSB’s investigation update (PDF).

The plant was operating under normal conditions on the night of the incident until high vibration triggered the automatic shutdown of one of two reflux pumps operating at the time, the CSB report explains. Dow personnel returned the pump to operation within a couple of minutes, though its vibrations remained higher than normal. Over the next couple of hours, “numerous upsets” to the EtO finishing process triggered high-level alarms in the reflux drum, CSB notes. Operators worked to stabilize the level in the drum until an explosion occurred in its vicinity. The initial explosion was followed by a fire and another explosion of the reflux drum itself, which was about half full of liquid EtO at the time. No injuries were linked to the incident, but it caused substantial damage to the plant and hundreds of residents living within a half-mile of the facility were ordered to shelter in place that night.

“At the time of the incident, the reflux drum was equipped with an emergency pressure-relief valve, but the valve was unable to prevent the reflux drum from exploding,” CSB’s report states.

The agency’s findings so far have prompted investigators to further examine the design of the reactive material emergency pressure-relief system as well as maintenance procedures and practices.

CSB’s investigation is ongoing. More information can be found in the agency’s press release, and future updates will be available via the incident page on the CSB website.

Related: In March 2024, EPA issued a final rule that adopts stricter standards for air toxics emissions from commercial facilities that use EtO as a sterilization agent. Previously, an industrial hygienist who participated in the sampling of EtO emissions from a facility that used the gas to sterilize medical devices in an Illinois community discussed his experiences as part of a prerecorded virtual session at AIHce EXP 2020.