The US Chemical Safety and Hazard Investigation Board (CSB) shared preliminary findings from its investigation into the fatal release of a highly toxic gas at a paper mill earlier this year. That reacted with the sulfur compounds in the acid sewer piping and generated toxic hydrogen sulfide gas. Instead, the hydrogen sulfide gas flowed through piping connected to the scrubber into two process vessels located elsewhere in the building. From those vessels, the toxic gas flowed and escaped through holes and process openings in equipment within the Kraft Mill. That flushed the accumulated chemicals past the upward transition, and the remaining toxic gas in the building dissipated about three hours after the scrubber fan had been turned off and the release began.