What was found
DURING CRUISE FLIGHT, CREW REPORTED A WHISTLING SOUND FROM THE MAIN ENTRY DOOR IN THE CABIN, FOLLOWED BY A RUSH OF AIR AND PRESSURIZATION LOSS AT A 2000 FPM RATE. EMERGENCY WAS DECLARED, THE PASSENGER O2 MASKS WERE DEPLOYED AND AN EMERGENCY DESCENT WAS INITIATED. THE ACFT LANDED SAFELY. MX FOUND PRIMARY DOOR SEAL DAMAGED AND REPLACED SEAL.