AN ASTRA G100 AT FL390 HAD DOOR WARNING LIGHT AND HEARD LOUD SQUEAL FROM DOOR SEAL. MADE EMER DSCNT FROM FL390. DOOR LIGHT WENT OUT AND SQUEAL STOPPED. CONTINUED FLT TO PLANNED ARPT AT FL190.

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WE WERE CRUISING AT FL390 WHEN WE HAD A CABIN DOOR LIGHT COME ON. THE LIGHT ON THIS PLANE MEANS AN UNSAFE DOOR OR LOSS OF PRESSURE TO THE DOOR SEAL. BECAUSE OF THE POSSIBILITY OF A BLOWN SEAL; WE ASKED FOR AN EMER DSCNT. THERE WAS A LOT OF NOISE COMING FROM THE DOOR SEAL AND IT WAS VERY HARD TO EVEN COM OVER THE RADIOS. WE WERE INITIALLY GIVEN DSCNT TO FL240 AND THEN TO 17000 FT. IN THE DSCNT; AS DIFFERENTIAL CABIN PRESSURE DECREASED; THE DOOR SEAL NOISE DISAPPEARED AND THE CABIN DOOR LIGHT WENT OUT. WE DECIDED TO CONTINUE TO OUR DEST AT FL190; AND CONTINUED TO ZZZ WITHOUT INCIDENT. AS FAR AS I CAN TELL; THERE WAS NO INDICATION OF CONFLICT FROM ATC AND WE SAW NO TFC ON TCAS DURING OUR DSCNT. WE ARE WORKING WITH TECHNICAL SUPPORT FROM MAINT AND IT APPEARS THE PROB IS A RESTR IN THE PRESSURE LINE TO THE DOOR SEAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE DOOR SEAL PROB WAS FOUND TO BE CAUSED BY A SEAL PRESSURE LINE AND LINE FILTER THAT WAS FOUND BLOCKED BY WATER. THE RPTR WAS UNAWARE OF THE SEAL INFLATION LINE OR OF ANY ROUTINE MAINT OF THIS LINE FILTER.