C560 CREW WAS REQUIRED TO MAKE AN EMER DSCNT BECAUSE OF A CABIN DOOR SEAL FAILURE.

Narrative

FLT FROM MDW-SOP. HAD AN ANNUNCIATOR LIGHT ILLUMINATE INDICATING A FAILED CABIN DOOR SEAL. ABOUT 1 MIN LATER (AFTER COMPLETING CHKLIST ITEMS); HEARD A LOUD 'POP' AND THE SOUND OF AIR BLOWING AT THE DOOR. ADVISED CTR THAT WE HAD A DOOR SEAL FAIL AND THAT WE NEEDED TO DSND. STARTED A PRECAUTIONARY EMER DSCNT TO 15000 FT. CTR GAVE US AN ALT OF FL350 AND WE AGAIN ADVISED WE NEEDED TO GET DOWN. THEY ASKED HOW LOW; WE SAID 15000 FT. THEY CLRED US DOWN TO 15000 FT AND WE OPTED TO LAND AT GSO WHICH WAS NEAREST SUITABLE ARPT INSTEAD OF CONTINUING TO SOP. CABIN DID NOT LOSE PRESSURE RAPIDLY; NO FURTHER SVCS WERE REQUESTED FROM ATC OR CFR PEOPLE ON THE GND. LNDG UNEVENTFUL. PLANE WAS PUT INTO THE SVC CTR FOR REPAIR. OUTCOME UNKNOWN AT THIS TIME. HOW PROB AROSE: UNKNOWN (POSSIBLY INADEQUATE SEAL. HIGH HUMIDITY AT DEP 90 DEGS F TO -60 DEGS C AT ALT MAY HAVE CAUSED ICE ON SEAL). CORRECTIVE ACTIONS: CHKLIST AND PRECAUTIONARY EMER DSCNT. DECISION: TOOK THE MOST SAFE OPTION OF PRECAUTIONARY DSCNT AND LNDG AT NEAREST SUITABLE ARPT. ACTIONS: PLTS ALREADY WERE WEARING OXYGEN DUE TO CHKLIST FOR 'DOOR SEAL' ANNUNCIATOR. OPTED TO ALSO DROP THE PAX MASKS AS A PRECAUTION. ALSO KEPT PAX INFORMED ALONG THE WAY TO EASE THEIR ANXIETY. FACTORS AFFECTING HUMAN PERFORMANCE: 1) INADEQUATE CHKLISTS THAT LEAVE LOTS OF GRAY AREAS IN DEALING WITH POTENTIAL EMERS. 2) DIFFICULTY IN CREW COM WITH OXYGEN MASKS ON.