A B747-100 FREIGHTER DIVERTS TO SHEMYA WHEN THEIR SMOKE DETECTOR ALERTS THE CREW TO A PROB. STRONG FUMES WERE THEN SENSED BY THE CREW IN THE CARGO AREA PRIOR TO THE DIVERSION TO ALTERNATE.

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IN SUM: A B747-100 FREIGHTER DIVERTS TO SHEMYA WHEN THEIR SMOKE DETECTOR ALERTS THE CREW TO A PROB. STRONG FUMES WERE THEN SENSED BY THE CREW IN THE CARGO AREA PRIOR TO THE DIVERSION TO ALTERNATE. THE FLT HAD BEEN ENRTE FROM NARITA TO ANC; AK. THE CHOICE OF SHEMYA WAS BASED UPON WX; DISTANCE; RWY LENGTH AND ACFT HANDLING FACILITIES. THE CREW COULD NOT ACTUALLY SEE ANY SMOKE SO THE SO AND THE CAPT TOOK TURNS IN GOING AFT TO THE SOURCE OF THE STRONG FUMES ON THE MAIN DECK. THE FUMES WERE STRONG ENOUGH FOR THE CAPT TO FEEL THAT AN EMER SHOULD BE DECLARED. THEY WERE 'CAUSTIC' AND 'CREATED A BURNING SENSATION' TO THE LUNGS. THE LNDG WT AT SYA WAS 560000 LBS; 5000 LBS UNDER MAX LNDG WT. ZAN HAD RELAYED THE CREW'S MESSAGE FOR AIRSTAIRS TO BE PLACED FOR THE CREW'S IMMEDIATE EXIT AT SYA. THE CAPT BRIEFED THE FIRE CREW OF 2 MEN AND THEY THEN INSPECTED THE REAR AREA FOR 30 MINS; UNTIL THEIR PORTABLE AIR RAN OUT. THE CAPT ALSO BRIEFED A STATE TROOPER TO MAINTAIN ACFT AND PERSONNEL SECURITY; MAINTAINING ACFT AND CREW INTEGRITY SO THAT THE CUSTOMS PROC IN ANC WOULD NOT BE CONSIDERED CONTAMINATED BY THE STOP AT SYA. LATER; CUSTOMS ACCEPTED THAT PROC. THE CAPT AND THE FIRE FIGHTER WENT BACK ON BOARD THE ACFT AND 'SNIFFED' THE AREA FOR FUMES; BREAKING OPEN THE VISQUEEN COVERING FOR THAT PURPOSE. THEY COULD STILL SENSE A SMELL OF PLASTIC LIKE ODORS; BUT NOT AS STRONG. THERE WERE SOME DROPLETS RUNNING DOWN INSIDE THE VISQUEEN COVERING. THE CAPT ATTRIBUTED THAT TO THE WARMER PACKAGES NOW ENCOUNTERING THE COLD AIR AT THE ARPT; NEAR 0 DEGS F IN TEMP. THE FIRE FIGHTER DECIDED TO 'HOSE' ONE PALLET WITH WATER AND A 3% MIX OF AFFF; FOLLOWED BY A BURST OF FOAM. THE SO AND THE CAPT WENT TO THE LCL MEDICAL FACILITY FOR A CHK-UP. THE CARGO IN QUESTION WAS A PALLET OF NOTEBOOK COMPUTERS; WITH NOTHING UNUSUAL NOTED ABOUT THE BOXES. NO MORE STRONG FUMES NOTED. MAINT PERSONNEL FROM COLD BAY WERE FLOWN IN AND INSPECTED THE ACFT. THE SMOKE DETECTOR IN THE QUESTIONED AREA WAS DEACTIVATED AND THE CREW TOOK THE FLT ON TO ANC. THERE WERE DEADHEADING MECHS ASSIGNED TO BE IN THE REAR OF THE ACFT TO CHK ON ANY FURTHER PROBS. CAPT BELIEVES THAT THE SMOKE DETECTOR SENSED THOSE STRONG FUMES AND REACTED ACCORDINGLY.