Abstract: At approximately 9:34 a.m. on January 10, 2025, an employee was directed to enter a 23,737-gallon rail tank car containing residues of PCBs and transformer oil to obtain wipe samples of the interior surfaces. The rail tank car was a permit-required confined space. The employee wore a full-face air-purifying respirator, chemical protective suit, boots, and gloves. Shortly after descending the temporary ladder to the tank bottom, the employee slowed, then fell forward and became unresponsive at the base of the ladder. Prior to entry, the tank car had not been mechanically ventilated, atmospheric monitoring was insufficient and not performed during entry, and non-entry rescue systems were inadequate-the tripod lacked a mechanical winch or lifeline, and the entrant was not wearing a full-body rescue harness. Oxygen levels inside the tank were as low as 5%, resulting in fatal asphyxiation.