CSB Findings Prompt City to Update Code for Pressure Vessel Inspections

St. Louis revised its Mechanical Code to standardize in-service inspections after a fatal 2017 industrial explosion.

Jan. 27, 2026

2 min read

Employees inspect by taking photographs of internal pressure tanks in confined spaces.

The U.S. Chemical Safety and Hazard Investigation Board said St. Louis has implemented new requirements for in-service inspections of boilers and pressure vessels, following recommendations issued after the 2017 explosion at the Loy-Lange Box Company.

According to the CSB, the St. Louis Board of Aldermen approved revisions to the city’s Mechanical Code that adopt national consensus standards for pressure vessel inspections and establish minimum qualifications for inspectors. The updated ordinance took effect Nov. 15, 2025.

The changes require that in-service inspections be conducted in accordance with the National Board Inspection Code and performed by inspectors commissioned under the National Board of Boiler and Pressure Vessel Inspectors’ in-service inspection program, the CSB said.

The CSB’s recommendations stem from its investigation into the April 3, 2017, explosion at Loy-Lange in St. Louis, when a pressure vessel catastrophically failed. According to the agency, the incident resulted in four fatalities after the vessel was ejected from the building and struck a neighboring facility.

The CSB issued its final investigation report in July 2022 and recommended that the city update its Mechanical Code to strengthen oversight of in-service pressure vessel inspections. With the ordinance now in effect, the CSB said two of its recommendations to the city have been closed.

According to the agency, the remaining open recommendation calls for broader communication of the investigation’s findings to stationary engineers and registered boiler and pressure vessel owners within the city.

The city’s regulatory action comes as Congress approved $14 million in fiscal 2026 funding for the CSB, according to Safety+Health magazine, a publication of the National Safety Council. The funding, which runs through Sept. 30, was included in a broader appropriations package passed by wide margins in both the House and Senate, the publication reported.

The Trump administration has long sought to eliminate the agency despite its modest operating budget and crucial role in investigating major chemical incidents and issuing safety recommendations nationwide.

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