Abstract: At 8:15 p.m. on May 25, 2018, Employee #1 was power washing the outside of the semi-truck tanker trailer. The employee entered the tanker trailer to wash the inside and was not found for two hours. The fire department was called to rescue the employee. Atmospheric monitoring found atmospheric levels of hydrogen sulfide at 100 ppm and hydrogen cyanide at 30 ppm. No written evidence of atmospheric monitoring was available following the employee's recovery from the space, and no ventilation of the space prior to or during the entry was performed. No attendant or entry supervisor was assigned to the entry. Employee #1's death was determined to be chemical asphyxia by vitiated atmosphere with hydrogen sulfide and hydrogen cyanide gasses.