TWO PORTABLE FIRE EXTINGUISHERS FAIL WHILE FIGHTING SMOKE IN ACFT LAVATORY.

Narrative

FLT WAS SCHEDULED AS A NON STOP TRIP FROM MIA TO BOS; BUT BECAUSE OF ACFT STRUCTURAL WT LIMITATIONS; HAD TO MAKE A PLANNED FUEL STOP AT BWI. THE FLT WAS NORMAL IN ALL OTHER RESPECTS. APCHING PROVIDENCE DURING DSCNT THE AFT F/A NOTIFIED THE COCKPIT THAT THERE WAS SMOKE IN THE AFT LEFT LAV AND THAT THE SMOKE ALARM HAD GONE OFF. SHE SAID SHE THOUGHT SOMEONE HAD THROWN A CIGARETTE IN THE TRASH BIN AND SHE WANTED TO USE A FIRE EXTINGUISHER ON IT. I CONCURRED AND ALSO SENT THE S/O BACK TO SEE WHAT WAS HAPPENING. WHEN THE S/O RETURNED A FEW MINS LATER HE SAID THERE WAS NO MORE SMOKE AND NO SCORCHING; BUT SOME BURNED PAPER IN THE ASH TRAY. THE F/A'S HAD USED 2 WATER AND 2 HALON FIRE EXTINGUISHERS. ONE WATER AND ONE HALON EXTINGUISHER DID NOT WORK. SINCE THE SITUATION WAS WELL UNDER CTL; ACCORDING TO RPTS FROM BOTH THE S/O AND THE SENIOR F/A; I ELECTED TO CONTINUE TO BOS. I TURNED ON THE NO SMOKING SIGN SINCE WE ONLY HAD THE COCKPIT FIRE EXTINGUISHER AND ACFT WATER AVAILABLE TO FIGHT ANY FURTHER FIRES. UPON ARR AT BOS I PERSONALLY INSPECTED THE AREA AND SAW NO SIGNS OF FIRE. I DON'T BELIEVE THERE WAS ENOUGH HEAT GENERATED TO DISCHARGE THE TRASH BOX FIRE EXTINGUISHER. I ALSO INSPECTED THE CO2 CARTRIDGE IN THE WATER FIRE EXTINGUISHER THAT FAILED--IT HAD BEEN PUNCTURED BUT I COULD NOT DETERMINE WHETHER OR NOT IT WAS A FRESH PUNCTURE. THE F/A'S PERFORMED IN AN EXEMPLARY MANNER AND SHOULD BE COMMENDED FOR THEIR ACTIONS IN THIS POTENTIALLY SERIOUS INCIDENT. AFTER DEPLANING A FAMILY APCHED THE SENIOR F/A IN THE TERMINAL AND SAID THEY THOUGHT THEIR YOUNG SON WAS RESPONSIBLE FOR THE SMOKE IN THE LAV. SUPPLEMENTAL INFO FROM ACN 84767: I BELIEVE THE F/A'S SHOULD HAVE NOTIFIED THE COCKPIT SOONER. I AM CONCERNED THAT THIS POTENTIALLY HAZARDOUS SITUATION WILL HAPPEN MORE OFTEN WHEN THE NO SMOKING LAW GOES INTO EFFECT.