EMER DSCNT INITIATED BY THE FLT CREW OF A C501 WHEN THE DOOR SEAL BLEW AT 17000 FT WITH A DIVERSION TO LGB; CA.

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PICKED UP 2 PAX AT MOD. CLBING OUT OF 17000 FT; THE DOOR SEAL BLEW CAUSING DECOMPRESSION. EMER PROCS WERE FOLLOWED. AFTER PUTTING ON OXYGEN AND DSNDING; WE DECIDED TO LAND AT NEAREST SUITABLE ARPT; LGB. AT LGB; CITATION MAINT IDENTED THE PROB AS A FAILED PRESSURE REGULATOR FOR THE DOOR SEAL. THIS REGULATOR IS NOT LIFE LIMITED; NOR IS IT CHKED DURING THE VARIOUS PHASE INSPECTIONS. CESSNA MIGHT CONSIDER LIMITING THE REGULATOR'S LIFE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS CALLED TO DETERMINE IF ANY AGENCY HAD BEEN CONTACTED REGARDING THIS FAILURE. THE PIC HAD TALKED WITH THE MAINT PERSONNEL AT THE MANUFACTURER'S PLANT. THEY SAID THAT THIS INCIDENT WAS SUCH AN ISOLATED CASE THAT THERE WAS NOT A CONCERN ABOUT HAVING TO PLACE A 'LIFE LIMIT' ON THE PRESSURE REGULATOR. THIS WAS A VERY RARE CASE WHEREIN THE DIAPHRAGM ASSOCIATED WITH THE REGULATOR/SEAL SYS WAS STUCK IN THE PARTIALLY OPEN POS; THEREBY NOT ALLOWING FULL PRESSURIZATION OF THE DOOR SEALS AROUND THE ENTRANCE DOOR. THE SEALS WERE SUBJECT TO INTERNAL AS WELL AS EXTERNAL PRESSURES AND WERE TORN OFF THE TRACK HOUSING; ALLOWING THE RAPID DECOMPRESSION. IT WAS NOT VIEWED AS A FAILURE OF THE PRESSURE REGULATOR ITSELF.