The efforts of the U.S. Chemical Safety Board (CSB) investigators to determine the cause of last week’s fatal workplace explosion in St. Louis, Missouri have been hampered by the facility’s lack of structural integrity, which have made it too dangerous to inspect in the days after the incident.

Four people were killed when a hot water storage tank at Loy-Lange Box Co. exploded through the company’s roof and went airborne, flying 500 feet before crashing into an office at Faultless Linen, killing three people there. The fourth fatality was at Loy-Lange.

Early reports that the explosion involved a boiler were inaccurate, according to the CSB, which indicated that the item in questions was a semi-closed receiver, or SCR. "This tank was part of a steam generator system that serves the same purpose as a boiler, but is of a different design," the CSB said in a statement.

CSB have been able to visit all three sites impacted by the April 3^rd incident: Faultless Linen; Pioneer Industrial Corp.; and Loy-Lange Box Company.

Early findings:

• The SCR launched out of the Loy-Lange facility and into the Faultless Linen site, crashing into an office area. An initial examination found that the vessel appears to have landed top down into a room where three people were present.
• The three people in the office room were fatally injured 
• The structural integrity of the Faultless Linen office area is still being assessed. The failure mode of the SCR is unknown. Currently, it is too dangerous to enter the room to conduct an in-depth examination.  The CSB has begun discussions with the appropriate entities on site to remove the equipment to allow forensic examination.
• An initial assessment also found that an approximately 12.5 foot long pipe, which had been attached to the SCR, crashed through the roof of the Pioneer facility. It stuck in the roof and punctured an office ceiling, where it remained until the company removed it to temporarily re-roof the hole to protect the building from water damage.
• Structural engineers retained by the CSB determined that the Loy-Lange site is not safe for CSB entry at this time. CSB investigators have photo-documented the perimeter. 
• The CSB is coordinating its investigation efforts with local emergency responders and other federal agencies and investigative entities.   
• CSB investigators are likely to remain on site for the next several days. Additional updates will be provided as the investigation develops. 

The CSB is an independent federal agency whose mission is to drive chemical safety change through independent investigations to protect people and the environment. The agency’s board members are appointed by the President and confirmed by the Senate. CSB investigations look into all aspects of chemical incidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems.