FLC OF A CANADAIR CL65 RETURNED TO LAND AFTER THE DOOR MASTER WARNING LIGHT ILLUMINATED.

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ON DEC/XA/00 FLT CVG-ABE; A PAX DOOR MASTER WARNING OCCURRED AT APPROX 2500 FT. WE LEVELED AT 3000 FT AND RETURNED FOR LNDG WHILE RUNNING THE QRH EMER PROC. THE PROC CALLED FOR SELECTION OF THE MANUAL MODE AND A FULL RATE INCREASE OF THE CABIN ALT. AFTER SELECTING THE INCREASE POS THERE WAS STILL A SLIGHT POSITIVE PRESSURE INDICATION OF APPROX -.2 DELTA P. THIS WAS OF CONCERN TO US AND I ELECTED FOR A DELAY VECTOR TO CALL MAINT AND CLARIFY IF THIS INDICATION WOULD CAUSE ANY PROBS UPON LNDG. I WAS UNDER THE IMPRESSION THAT UPON WT ON WHEELS; THE ACFT WOULD UNPRESSURIZE AS IT DOES NORMALLY IN AUTO MODE. THIS IS NOT THE CASE IT TURNS OUT. MAINT INDICATED THEY DIDN'T SEE ANY PROB. AFTER TAXIING THE ACFT TO THE GATE AND COMPLETING THE PARKING CHKLIST; THE FLT ATTENDANT SAID SHE WAS HAVING DIFFICULTY OPENING THE MAIN CABIN DOOR. IT DID NT OCCUR TO ME THAT THIS MAY HAVE BEEN PRESSURE RELATED. I WAS IN THE PROCESS OF GETTING UP TO HELP WHEN THE DOOR BASICALLY FLEW OPEN. SHE WAS HOLDING ONTO THE STEP/HANDLE AND FELL FORWARD WITH THE DOOR. SHE SUFFERED ONLY MINOR SCRAPES ON HER LEGS AND REQUESTED NO FIRST AID. I BELIEVE THAT I FOLLOWED THE QRH PROC CORRECTLY. IN ANY CASE; IF THE PRESSURE REMAINED ON THE ACFT DUE TO A FAULTY PRESSURE SYS OR AN INCORRECTLY RUN PROC; AN EMER DEPRESSURIZATION AFTER LNDG WOULD ENSURE THAT NO RESIDUAL PRESSURE COULD REMAIN UNLESS THERE HAPPENED TO BE A MAJOR MALFUNCTION OF THE OUTFLOW VALVES. SELECTION OF THE EMER DEPRESSURIZATION BUTTON WAS PREVIOUSLY INCLUDED IN THE QRH PROC; BUT WAS REMOVED FOR OTHER REASONS. IT WAS AT THE START OF THE CHKLIST FOR HIGH ALT SITS. IF IT WERE REINSERTED AT THE END AFTER LNDG; THIS WOULD ALLEVIATE THE PROB I INDICATED.