B757-200 FO REPORTS EMERGENCY DIVERSION TO NEAREST SUITABLE ARPT DUE TO ACRID FUMES.

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I WAS THE PLT MONITORING (PM); AND THE CAPT WAS THE PF. WHILE LEVEL AT FL400; THE PF NOTICED UNIDENTED; ACRID FUMES COMING FROM COCKPIT GASPER VENTS. PM CONFIRMED ACRID FUMES. IMMEDIATELY DONNED OXYGEN MASKS AND ESTABLISHED CREW COMS. THE PM CALLED FLT ATTENDANTS IN THE CABIN; WHO ALSO CONFIRMED PRESENCE OF FUMES. AS THE PM REFED QRH SMOKE AND/OR FUMES NON NORMAL PROC; PRESENCE OF FUMES CONTINUED TO INCREASE. FLT ATTENDANTS THEN RPTED BURNING EYES AND SOME THROAT IRRITATION AMONG PAX AND CREW. THE DECISION WAS MADE TO DECLARE AN EMER AND DIVERT TO THE NEAREST SUITABLE ARPT. EMER DSCNT WAS INITIATED. PAX AND CABIN CREW WERE INFORMED OF THE SITUATION. PM ASKED CENTER TO RELAY DIVERT INFO TO OUR COMPANY. PLTS SHARED THE WORKLOAD DURING DSCNT; AND PM CONTINUED TO ATTEMPT TO ISOLATE SOURCE OF FUMES USING THE QRH. NORMAL APCH AND LNDG WERE ACCOMPLISHED; FIRE AND RESCUE PERSONNEL INSPECTED THE ACFT; AND NO SMOKE NOR SIGNS OF FIRE WERE NOTED. THE DECISION WAS MADE NOT TO EVAC PAX OR CREW. TAXI TO APRON AND TUG TO GATE WAS NORMAL. PAX AND CREW DEPLANED NORMALLY.