What was found
PASSING FL310 TO FL340, HEARD A BANG & SAW CABIN ALTITUDE RISE. STARTED EMER DESCENT AS CABIN RISE AT A RATE OF 3,200FT/MIN. ABLE TO DESCEND 10,000FT . NOTICED NO AIRFLOW INTO CABIN DURING DESCENT & AN INCREASING TEMP. AFTER INSP & OPS CHKS, OPENED FORWARD FLOOR PANEL & FOUND TRANSITION DUCT SEPERATED FROM THE SUPPLY DUCT AT FLEXIBLE COUPUNG, INSPECTED & FOUND NO DAMAGE TO EITHER DUCTS FLANGES OR ANY SURROUNDING AREAS & REINSTALLED FLEXIBLE COUPLING IAW AMM 21•21-00, PERFORMED APU PRESSURIZATION & FOUND OUTFLOW VALVES TO NOT BE CLOSING FULLY. PERFORMED APU LEAK CHECK AGAIN & FOUND TEE FITTING LEAKING. TIGHTENED B-NUT ON MANUAL PRESSURIZATION LINE IAW AMM 21-30-00. LEAK & OPS CHECKED IAW AMM 21-30-00.