Narrative:

First officer started to smell acrid smell. Initially I did not smell fumes nor was there any smoke. The first officer continued to smell fumes; so I directed oxygen masks be put on. We established communications and ran the checklist for fumes in cockpit. After noting no smoke was seen yet; I had the first officer stay on oxygen while I investigated the smell throughout the cockpit. I found the smell had reduced slightly and was strongest in the outflow along the upper circuit breaker panel. There were no hot spots or popped breakers. We had been circumnavigating a long line of WX with a flight plan to fly over ZZZ prior to turning around the south end of the WX towards ZZZ1. With the long runways and the wind down the runway; we opted to plan the descent to land at ZZZ. We declared an emergency informing ATC that the problem had reduced but we desired emergency equipment standing by. We descended with the speed brakes open and lowered the gear upon reaching 10000 ft but we still landed 5000 pounds over maximum landing weight. Approach into ZZZ was uneventful to visual backed up with an ILS to runway 18R. Touchdown was soft and we rolled out 8000 ft. We taxied back to the ramp with emergency equipment following and no sign of smoke. Subsequent discussion with maintenance noted that the smell we had noted in the air ducts was also found in the #1 recirculation fan under the first officer's seat. Part of the checklist had that fan off in-flight.

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Original NASA ASRS Text

Title: B757 FLT CREW DECLARED EMER AND DIVERTED DUE TO ELECTRICAL FUMES IN COCKPIT.

Narrative: FO STARTED TO SMELL ACRID SMELL. INITIALLY I DID NOT SMELL FUMES NOR WAS THERE ANY SMOKE. THE FO CONTINUED TO SMELL FUMES; SO I DIRECTED OXYGEN MASKS BE PUT ON. WE ESTABLISHED COMS AND RAN THE CHKLIST FOR FUMES IN COCKPIT. AFTER NOTING NO SMOKE WAS SEEN YET; I HAD THE FO STAY ON OXYGEN WHILE I INVESTIGATED THE SMELL THROUGHOUT THE COCKPIT. I FOUND THE SMELL HAD REDUCED SLIGHTLY AND WAS STRONGEST IN THE OUTFLOW ALONG THE UPPER CIRCUIT BREAKER PANEL. THERE WERE NO HOT SPOTS OR POPPED BREAKERS. WE HAD BEEN CIRCUMNAVIGATING A LONG LINE OF WX WITH A FLT PLAN TO FLY OVER ZZZ PRIOR TO TURNING AROUND THE S END OF THE WX TOWARDS ZZZ1. WITH THE LONG RWYS AND THE WIND DOWN THE RWY; WE OPTED TO PLAN THE DSCNT TO LAND AT ZZZ. WE DECLARED AN EMER INFORMING ATC THAT THE PROB HAD REDUCED BUT WE DESIRED EMER EQUIP STANDING BY. WE DSNDED WITH THE SPD BRAKES OPEN AND LOWERED THE GEAR UPON REACHING 10000 FT BUT WE STILL LANDED 5000 LBS OVER MAX LNDG WT. APCH INTO ZZZ WAS UNEVENTFUL TO VISUAL BACKED UP WITH AN ILS TO RWY 18R. TOUCHDOWN WAS SOFT AND WE ROLLED OUT 8000 FT. WE TAXIED BACK TO THE RAMP WITH EMER EQUIP FOLLOWING AND NO SIGN OF SMOKE. SUBSEQUENT DISCUSSION WITH MAINT NOTED THAT THE SMELL WE HAD NOTED IN THE AIR DUCTS WAS ALSO FOUND IN THE #1 RECIRCULATION FAN UNDER THE FO'S SEAT. PART OF THE CHKLIST HAD THAT FAN OFF INFLT.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.