After the cracking temperature has been reached, the gas is quickly quenched in the heat exchanger to stop the reaction.

[12] The explosion was the first major incident in the plant's history, although there had been numerous leaks of flammable gases in recent years.

According to a report submitted by Williams Olefins to the Louisiana Department of Environmental Quality (DEQ), 514 pounds (233 kg) of propylene gas escaped.

[1] At the Williams Geismar Olefin Plant, propylene was extracted from a stream of hydrocarbon by heating the mixture in one of two reboilers, followed by fractional distillation.

Reboiler B, that ultimately failed, had been purged with nitrogen and isolated from process with a single closed block valve after maintenance activity in February 2012.

"[14] On December 11, 2013 OSHA cited Williams Olefins for six Process Safety Management standard violations, including one willful, and fined the company $99,000.

[15] Dorinda Folse, OSHA's Baton Rouge area director, said: "Williams Olefins violated safety and health standards which, when followed, can protect workers from hazardous chemicals.

"[16] The five serious violations, where there was "substantial probability that death or serious physical harm could result from a hazard about which the employer knew or should have known", were: The willful violation—defined as one "committed with intentional, knowing or voluntary disregard for the law's requirements, or with plain indifference to worker safety and health"—was the company's failure to develop clear, written procedures for how to change and put idle pressure vessels into service.

[16] The Chemical Safety Board issued a detailed report,[1] and some of the key lessons include: In the first civil trial regarding the explosion, four workers filed suit against Williams Olefins LLC and parent company Williams Companies, Inc. for their alleged negligence.