A C750 IN CRUISE AT FL450 DECLARED AN EMER AND DSNDED TO FL350 DUE TO CABIN ALT CLBING. CREW CORRECTED PRESSURE LOSS; CANCELED EMER AND RETURNED TO FL410. RPTR STATES LOSS OF PRESSURIZATION EVENT WAS THE RESULT OF MULTIPLE COMPONENT FAILURES.

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WHILE IN CRUISE AT FL450; WE GOT AN AMBER 'BAGGAGE DOOR SEAL' CAS MESSAGE AND RESPONDED BY ACCOMPLISHING THE CHKLIST ITEMS. AS THE CHKLIST STATES; WE MONITORED THE CABIN PRESSURE AND SINCE THERE WAS NO CHANGE; WE MAINTAINED ALT AND CONTINUED OUR MONITORING. THIS IS A FAIRLY COMMON CAS MESSAGE IN THE CX AND IS USUALLY FOLLOWED BY NO FURTHER PROBLEMS. I BELIEVE THIS IS WHY THE CHKLIST DOES NOT MANDATE AN ALT CHANGE UNLESS THERE IS AN ACTUAL CABIN PRESSURE LOSS. SOME TIME AFTER THE ORIGINAL MESSAGE; I ESTIMATE BETWEEN 20 AND 30 MINUTES; WE GOT THE AMBER 'BAGGAGE ALT' CAS MESSAGE AND NOTICED THE CABIN ALT INCREASING SHORTLY AFTER THE MESSAGE APPEARED. SINCE THE GREATER ISSUE WAS THE LOSS OF CABIN PRESSURE; WE IMMEDIATELY ACCOMPLISHED THE MEMORY ITEMS OF THE 'LOSS OF CABIN PRESSURE' CHKLIST. AS TRAINED; WITH A LOSS OF CABIN PRESSURE; WE DECLARED AN EMER AND BEGAN AN IMMEDIATE DSCNT TO A LOWER ALT. ONCE WE GOT THE LOSS OF CABIN PRESSURE AND EMER DSCNT MEMORY ITEMS COMPLETED; WE WERE LEFT WITH ENOUGH TIME TO ASK THE PAX TO REMAIN SEATED AND ENSURE THEIR SEATBELTS WERE FASTENED. ALL OF THIS WAS DONE PRIOR TO REACHING FL400 SO WE HAD ENOUGH TIME TO FURTHER ANALYZE THE SITUATION. THE CAUSE OF THE LOSS OF CABIN PRESSURE WAS OBVIOUS; SO WHILE STILL DSNDING; WE COMPLETED THE BAGGAGE ALT CHKLIST. PER THIS CHKLIST; WE CLOSED THE BAGGAGE ISOLATION VALVE; WHICH PNEUMATICALLY ISOLATED THE CABIN FROM THE BAGGAGE COMPARTMENT. AS EXPECTED; THE CABIN IMMEDIATELY STOPPED ITS CLB AND BEGAN TO STABILIZE. WE ARRESTED THE CABIN CLB AT A CABIN ALT OF JUST OVER 10000 FT; AND SEEING THE SITUATION STABILIZE; DECIDED TO STOP THE DSCNT AT FL350 TO ASSESS THE SITUATION. AFTER APPROX 5 MINUTES AT FL350; THE CABIN HAD ALREADY DSNDED BELOW 10000 FT AND WAS DROPPING. WE REMAINED THERE UNTIL THE CABIN WAS BACK TO ITS NORMAL DIFFERENTIAL OF 9.3 PSID AND THE CABIN WAS AT ITS NORMAL LEVEL. THE SITUATION STABILIZED; WE AGAIN TURNED TO THE CHKLIST WHICH STATES THAT THE MAXIMUM ALT ALLOWED WITH THE BAGGAGE COMPARTMENT UNPRESSURIZED IS FL410. AT THIS TIME; WE CANCELLED THE EMER BECAUSE THERE WAS NO LONGER AN EMER SITUATION. IN THE CITIATION X; A LOSS OF BAGGAGE ALT IS CONSIDERED AN ABNORMAL SITUATION; NOT AN EMER. THE EMER SITUATION THAT RESULTED WAS DEALT WITH PER OUR TRAINING; THEN CORRECTED BY SUBSEQUENT ANALYSIS AND APPLICATION OF THE PROPER CHKLIST. WE WERE IN CRUISE FLT; HAD A NORMAL CABIN ALT AND PRESSURIZATION SCHEDULE; AND WERE IN NO IMMEDIATE OR OTHER DANGER. I WENT BACK TO THE CABIN TO BRIEF THE PAX ON THE SITUATION AND TOLD THEM IT WAS POSSIBLE TO CONTINUE TO THE DEST IF THEY SO DESIRED. WE CLBED BACK TO FL410 AND CONTINUED THE FLT WITHOUT FURTHER INCIDENT.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT MAINT FOUND FOUR MECHANICAL FAILURES WHICH WERE A DIRECT CAUSE OF THE LOSS OF CABIN PRESSURE; IE; THE BAGGAGE DOOR SEAL WAS INFLATED IN FLT BY PNEUMATIC SYSTEM AIR AND WAS FOUND TO HAVE PINHOLE LEAKS; THE VALVE THAT CTLS THE DOOR SEAL PRESSURE HAD A HEATING BLANKET THAT PREVENTED THE VALVE FROM FREEZING AND THE HEATING BLANKET WAS DRAWING A VERY LOW AMPERAGE AND WAS REPLACED; AND THE VALVE FAILED TO CTL THE PRESSURE TO THE DOOR SEAL AND THE PRESSURE SWITCH IN THE PNEUMATIC LINE TO THE SEAL TRIGGERED THE EICAS MESSAGE 'BAGGAGE DOOR SEAL.' MAINT REPORTEDLY ALSO FOUND THE SUPPLY LINE TO THE SEAL CTL VALVE KINKED; LIMITING THE PNEUMATIC AIR TO THE CTL VALVE. THIS WAS REPORTED AS A COMMON PROBLEM WITH THIS AIRPLANE AND ONLY REQUIRES MONITORING THE CABIN ALT. THE RPTR INDICATED THE BAGGAGE COMPARTMENT IS PRESSURIZED FROM A SECOND CTLED ISOLATION VALVE THAT ALLOWS THE CABIN PRESSURE INTO THE BAGGAGE COMPARTMENT. THE RPTR STATED THAT AFTER A SHORT PERIOD OF TIME; THE EICAS 'BAGGAGE ALT' AMBER WARNING ILLUMINATED AND IT WAS NOTED THE CABIN ALT STARTED TO CLB. AN EMER WAS DECLARED AND AN IMMEDIATE DSCNT BEGAN. THE PROBLEM WAS REPORTEDLY THE LEAKING BAGGAGE DOOR SEAL AND THE 'BAGGAGE ALT' CHKLIST WAS ACCOMPLISHED WHICH REQUIRED CLOSING THE BAGGAGE ISOLATION VALVE WHICH ISOLATED THE CABIN FROM THE BAGGAGE COMPARTMENT. THE RPTR STATED THE CABIN PRESSURE STABILIZED; THE EMER WAS CANCELLED AND THE FLT CONTINUED AT THE MAXIMUM ALT PERMITTED WITH THE BAGGAGE COMPARTMENT UNPRESSURIZED.