The U.S. Chemical Safety and Hazard Investigation Board is urging EPA to review and update its 1993 study on hydrofluoric acid to determine whether existing risk management regulations for petroleum refineries are adequate to protect against catastrophic releases of HF. In a letter dated April 23, CSB explains that it has investigated two refinery incidents in the last four years where explosions elevated the threat of a possible release of HF or modified hydrofluoric acid. During the agency’s investigations, members of the communities surrounding the refineries expressed concerns regarding the adequacy of the risk management strategies for the use of hazardous chemicals like HF. Residents were also concerned about the effectiveness of community notification procedures in the event of a catastrophic release.  The incidents CSB refers to in its letter are the February 2015 explosion at the ExxonMobil Refinery in Torrance, Calif., and the April 2018 explosion and fire at the Husky Superior Refinery in Superior, Wis. Both the Superior and Torrance explosions “resulted from the inadvertent mixing of hydrocarbons with air inside the unit that found an ignition source,” according to a January 2019 update on CSB’s investigation of the Husky explosion. In both explosions, debris impacted equipment in surrounding units and caused fires and releases into the atmosphere. In Torrance, two workers were injured, and the explosion caused serious damage. In Superior, 36 people sought medical attention, including 11 refinery and contract workers. More information is available in CSB’s news release.