STRONG COCKPIT ODORS CAUSES CONCERN WITH THE FLT CREW OF A B737-500 AT FL350; WITH PIC MAKING DECISION TO DIVERT AND LAND AT MRY.

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ON FLT FROM ZZZ TO SFO; WE REACHED CRUISE ALT OF FL350 AND BEGAN TO SMELL AN UNFAMILIAR ODOR. THE ODOR SOON BECAME STRONG AND IT SEEMED TO BE COMING FROM THE GASPER VENTS. THE CAPT ASKED ATC FOR A DSCNT TO FL240 IN CASE WE HAD A BAD PACK. THE CAPT SENT OFF A MESSAGE TO MAINT CTL. WE RAN THE QRC FOR SMOKE/FUMES/ODOR AND REF ACTION. DURING THIS TIME; THE CAPT ALSO REQUESTED DIRECT ROUTING TO SFO. WE TRIED TO ISOLATE THE SMELL BY TURNING ONE PACK OFF AT A TIME AND STILL COULD NOT IDENT THE SOURCE OF THE SMELL. THE CAPT CALLED THE PURSER UP TO THE COCKPIT TO SEE WHAT HE THOUGHT OF THE SMELL. THE PURSER SAID HE COULD ALSO SMELL IT IN FIRST CLASS. AT THE TIME WHEN MAINT COORD FINALLY RESPONDED TO OUR ACARS; THE SMELL BECAME VERY STRONG AND WE DECIDED TO CONTACT DISPATCH TO TELL THEM WE WERE PROCEEDING TO MRY FOR A PRECAUTIONARY LNDG. THE FLT ATTENDANTS PREPARED THE CABIN FOR LNDG AND I RECEIVED CLRNC FROM ATC TO GO TO MRY. THE CAPT SENT AN ACARS TO DISPATCH TO TELL THEM OF OUR DIVERSION AND DISPATCH SENT US A MESSAGE TO CONTACT THEM ON THE GND. THE CAPT AND I THEN BEGAN TO SET UP FOR LNDG IN MRY AND FINISHED ALL APPLICABLE CHKLISTS FOR OUR DSCNT AND APCH FOR LNDG. THE LNDG WAS UNEVENTFUL. ONCE THE ENGS WERE SHUT DOWN AND THE PARKING CHK COMPLETE; THE CAPT OPENED HIS SIDE WINDOW TO SPEAK TO THE COMPANY AGENT WHO WAS STANDING ON THE GND. THE AGENT SAID HE COULD SMELL THE ODOR COMING FROM THE COCKPIT. THE PAX AND THE CREW DEPLANED VIA AIRSTAIRS WITHOUT EVENT. PAX FROM FIRST CLASS COMMENTED AS THEY WERE DEPLANING THAT THEY TOO COULD SMELL THE ODOR WHEN WE WERE INFLT. I FEEL THAT THE CAPT AND I RESPONDED TO THIS EVENT IN THE APPROPRIATE MANNER IN WHICH WE HAVE TRAINED FOR. SUPPLEMENTAL INFO FROM ACN 618654: THE ODOR BECAME STRONG ENOUGH TO CAUSE GRAVE CONCERN FOR THE SAFE CONDUCT OF FLT. I LANDED THE ACFT. SUPPLEMENTAL INFO FROM ACN 619027:I SAW THE FIRST MESSAGE STATING: GETTING VERY FOUL SMELL IN COCKPIT; SEEMS TO BE COMING FROM GASPERS. NO SMELL IN CABIN/NO SMOKE IN COCKPIT. I SENT A MESSAGE TO FLT 'ARE YOU DECLARING AN EMER. DO YOU WANT EQUIP?' FOLLOWED BY A SECOND MESSAGE TO THEM; 'CALL ME WITH DETAILS ON THE GND.' FLT ABC MUST HAVE BEEN SENDING ME A MESSAGE DECLARING PRECAUTIONARY FOR ODOR IN COCKPIT. LNDG MONTEREY. NEXT MESSAGE FROM THEM WAS IN RESPONSE TO MY ACARS TO THEM; 'YES; DIVERTING TO MRY;' FOLLOWED BY 'NO EQUIP PRECAUTIONARY.' AT THIS POINT; I FELT IT WAS BEST NOT TO CONTACT FLT BY RADIO; SINCE WE HAD CLR COM BY ACARS AND THEY WERE BUSY TRYING TO FLY THE AIRPLANE. CAPT CONTACTED ME SHORTLY AFTER LNDG AND TOLD ME THEY HAD BEEN ON THE OXYGEN MASKS SINCE THEY DIDN'T KNOW IF THIS ODOR MAY HAVE SOME KIND OF PHYSICAL EFFECT ON THEM.