AN ACR MD80 CREW CHOSE TO DIVER LAND WITH A SULFUR SMELLING SMOKE HAZE IN THE CABIN. EMER DECLARED. EMER CRASH ALERT ACTIVATED.

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APPROX 100 MI NW OF STL; WE WERE INFORMED THAT THE SMELL OF SMOKE WAS IN THE CABIN AREA. ALL FLT ATTENDANTS NOTICED IT AS WELL AS ALL PAX. THEY SAID THAT IT HAD A LITTLE SMELL OF SULFUR. I WENT BACK TO ASSESS THE SIT. I NOTICED THE SMELL AS SOON AS THE COCKPIT DOOR WAS OPENED. I DID NOT NOTICE THE SMELL OF SULFUR BUT OF JUST SMOKE. THERE WAS A LITTLE HAZE IN THE CABIN. I HAD THE FLT ATTENDANT FEEL THE FLOOR AS WELL AS ALL OVERHEAD BINS FOR WARM SPOTS. THE SMOKE DISSIPATED IN APPROX 5 MINS WITH NO VISIBLE SMOKE. WE ASSUMED THAT A PAX MUST HAVE LIT A CIGARETTE AND I MADE A PA REQUESTING WHOEVER DID THAT ADMIT TO A FLT ATTENDANT WITH NO REPERCUSSIONS. IN APPROX 15 MINS AFTER THAT; THE SMOKE AND SMELL RETURNED FOR APPROX 5 MINS. ALL ELECTRICAL LOADS WERE NORMAL AND WE DID HAVE AIRFOIL ANTI-ICE ON AT THAT TIME. WE TRIED TO ISOLATE THE PROB WITH THE AIRFOIL ANTI-ICE SYS. WE WERE ALSO INFORMED THAT IT APPEARED THAT EVERY TIME THE SEAT BELT SIGN WAS CYCLED THAT THE SMOKE REAPPEARED. THE SMOKE DISSIPATED IN 5 MINS. I WAS STILL NOT CONVINCED THAT IT WAS A FIRE; EITHER ELECTRICAL OR OTHERWISE; BECAUSE IT KEPT DISSIPATING. THE ONLY THING WE DID NOT ALTER WERE THE AIR-CONDITIONING SUPPLY SWITCHES. AFTER ABOUT 15 MORE MINS; THE SMELL REAPPEARED AGAIN; SO WE DECIDED TO DECLARE AN EMER AND DIVERT TO LIT. DURING THE APCH; THE FLT ATTENDANTS NOTICED IT AGAIN AND ALSO ON THE GND SEVERAL TIMES. CFR TRUCKS WERE REQUESTED AND WE WENT THROUGH THE EMER LNDG PROC MINUS HAVING THE FLT ATTENDANTS GOING THROUGH THEIR PROCS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR DOES NOT KNOW WHAT CAUSED THE ODOR; MOSTLY OF SULFUR. IT DID NOT SMELL LIKE AN ELECTRICAL PROB. BOTH AIR-CONDITIONING PACKS WERE WORKING WITH NORMAL TEMP INDICATIONS. THE RPTR REGRETS THAT HE DID NOT TURN OFF THE HIGH PRESSURE BLEEDS.