What was found
(CAN) AIRCRAFT EN ROUTE WHEN PRESSURE BEGAN DECREASING AT UNCONTROLLABLE RATE. OXYGEN MASKS DEPLOYED AND DONNED, AIRCRAFT LANDED SAFELY AT ALTERNATE SITE. MAINTENANCE FOUND MOISTURE TRAPPED IN DOOR SEAL AIR SUPPLY LINE. PURGED AIR USING LT ENGINE TO SUPPLY BLEED AIR AND MANUALLY ACTIVATING PLUNGER TO ALLOW AIR TO FLOW FREELY THROUGH SEAL. AIRCRAFT TT: 2,277 HOURS.