Abstract: EMPLOYEE #1 DESCENDED THROUGH A 16 INCH DIAMETER ACCESS OPENING INTO AN UNVENTILATED ABOVE-GROUND (10 1/2 FEET DEEP, 33 FEET LONG) 20,000 GALLON LEADED GASOLINE STORAGE TANK. HE WAS WEARING A REXNORD (BIOMARINE) BIO PAK 45 CLOSED CIRCUIT BREATHING APPARATUS. HIS JOB WAS TO CLEAN SLUDGE FROM THE BOTTOM OF THE TANK (SUB-CONTRACT JOB). WITHIN ONE MINUTE OF ENTRY, THE EMPLOYEE WAS SEEN TO COLLAPSE, FACE DOWN, INTO 1 1/2 INCH OF SLUDGE AND LEADED GASOLINE. THE EMPLOYEE WAS NOT EQUIPPED WITH A SAFETY BELT (OR HARNESS) OR A LIFELINE. A CO-WORKER IMMEDIATELY CLIMBED INTO THE TANK (WITHOUT ANY RESPIRATORY PROTECTION) AND ATTEMPTED TO TIE A ROPE AROUND THE 6 FOOT, 185 POUND INDIVIDUAL. HE WAS UNSUCCESSFUL, AND NEARLY OVERCOME BY FUMES AND/OR OXYGEN DEFICIENCY HIMSELF DURING HIS SECOND DESCENT. RESPONDING FIRE FIGHTERS FOUND NO PULSE ON EMPLOYEE #1. THEY REMOVED HIM FROM THE TANK AND ADMINISTERED 100% OXYGEN AND CPR. HOWEVER, THE EMPLOYEE WAS PRONOUNCED DEAD ON ARRIVAL AT A LOCAL HOSPITAL.THE OUTSIDE TEMPERATURE WAS 14 DEGREES F. A PRELIMINARY AUTOPSY INDICATED DEATH WAS DUE TO AN OXYGEN DEFICIENCY. THE TANK PROBABLY HAD A HYDROCARBON ENRICHED ATMOSPHERE, DISPLACING THE OXYGEN CONTENT.