Abstract: On March 5, 1984, Employee #1 and two coworkers were working at a mining operation southwest of Riddle, OR. They lowered a Briggs-Stratton 3-horsepower gasoline-powered pump about 20 feet into the 35 foot deep mine shaft. The motor ran for 30 to 45 minutes, then quit. A coworker went into the shaft to restart the motor, but he could not keep it running and returned to ground level. Employee #1 then entered the shaft while the coworker primed the pump. The coworker heard a thud, and went to summon emergency help when Employee #1 did not respond to his calls. The second coworker reportedly went down into the mine shaft after Employee #1, but could not recall coming out. Emergency rescue operations took place after air-supplied breathing apparatus was obtained from the fire department. Employee #1 was pronounced dead at the scene. The county medical examiner determined the cause of death to be carbon monoxide poisoning.