What was found
IN LEVEL FLIGHT AT FL340 THE CABIN ALTITUDE ROSE ABOVE 10,000 FEET. CREW PERFORMED AN EMERGENCY DESCENT, COMPLIED WITH COM, UTILIZED THE RED BORDERED CHECKLIST, AND DIVERTED TO DEN. CABIN PRESSURE WAS REGAINED AT FL180 BUT CABIN MASKS HAD DEPLOYED. LANDING WAS UNEVENTFUL AND MAINTENANCE AT DEN REPLACED THE LEFT TURBINE NOZZLE SHUTOFF VALVE, THE LEFT AUGMENTATION VALVE, AND BOTH WATER SEPARATOR ICE SCREENS. THE AIRCRAFT HAS RETURNED TO SERVICE.