Abstract: At 7:00 a.m. on August 22, 2022, Employee #1 was operating an excavator at a hazardous waste treatment and disposal facility. Employee #1 was working in the Solids Processing Unit and was following a batch sheet recipe to mix neutralizing agents with industrial waste. Employee #1 went to the Liquids Processing Unit and asked a coworker to send spent sulfuric acid "pickle liquor" to the bay where he was working. Employee #1 returned to his excavator so he could mix the batch when the "pickle liquor" was sent. Moments after the "pickle liquor" was sent, Employee #1's excavator swung into the sidewall of the Solids Processing Unit. Employee #2 rushed over to see what happened and found Employee #1 unconscious. When Employee #2 attempted to climb up into the excavator to help Employee #1, he became lightheaded and lost consciousness. However, Employee #2 was able to regain consciousness and go for help and 9-1-1 was contacted. Additional coworkers arrived to assist Employee #1, including Employees #3 and #4. Employee #1 was transported to the hospital and treated for respiratory chemical exposure, but was declared brain dead on August 24, 2022, and died the following day. Employees #2, #3 and #4 were observed at the hospital and released the same day with no diagnosed injuries. It is unknown what chemical the employees were exposed to but was suspected to be hydrogen sulfide.