Narrative:

The chief purser called the cockpit to report an odor which smelled like burnt rubber. I asked her if there was any smoke and she said no. She had asked earlier during the flight a couple of times to warm up the cabin. It was indicating a normal 76 degrees; however; we warmed it up to eventually 80 degrees. I suspected she might be smelling heat from the packs so we lowered the temperature. I had her call me back in a couple of mins and she stated the smell had subsided. A few mins later she called back to say the smell was there again. I also reaffirmed that there was no smoke. Again we adjusted the cabin temperature. Everything appeared normal with the system. A third very concerned call came from her. She stated that the smell was a lot worse and that all 4 flight attendants agreed as well as a number of passenger. The smell was in the back around row 22. Even though there was no smoke; we decided the wisest alternative would be to get the airplane on the ground. ZZZ was about 100 mi off the nose and we were at FL350. Since I couldn't be sure that a burnt smell wouldn't escalate into smoke; I decided to declare an emergency; have equipment standing by; and plan a precautionary landing. I immediately notified dispatch. We also reviewed any applicable checklists. We did a cabin advisory and landed visually. I had the fire department inspect the outside of the aircraft and later the inside at the gate. Maintenance replaced a hot air valve and we dispatched to ZZZ2. I feel the crew used good CRM communication skills. We were well informed and feel that the flight attendants are a valuable tool in recognizing abnormalities. We arrived 3 hours late into ZZZ2; however; received numerous compliments from the passenger.

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Original NASA ASRS Text

Title: A320 DIVERTS DUE TO A BURNING SMELL IN THE CABIN.

Narrative: THE CHIEF PURSER CALLED THE COCKPIT TO RPT AN ODOR WHICH SMELLED LIKE BURNT RUBBER. I ASKED HER IF THERE WAS ANY SMOKE AND SHE SAID NO. SHE HAD ASKED EARLIER DURING THE FLT A COUPLE OF TIMES TO WARM UP THE CABIN. IT WAS INDICATING A NORMAL 76 DEGS; HOWEVER; WE WARMED IT UP TO EVENTUALLY 80 DEGS. I SUSPECTED SHE MIGHT BE SMELLING HEAT FROM THE PACKS SO WE LOWERED THE TEMP. I HAD HER CALL ME BACK IN A COUPLE OF MINS AND SHE STATED THE SMELL HAD SUBSIDED. A FEW MINS LATER SHE CALLED BACK TO SAY THE SMELL WAS THERE AGAIN. I ALSO REAFFIRMED THAT THERE WAS NO SMOKE. AGAIN WE ADJUSTED THE CABIN TEMP. EVERYTHING APPEARED NORMAL WITH THE SYS. A THIRD VERY CONCERNED CALL CAME FROM HER. SHE STATED THAT THE SMELL WAS A LOT WORSE AND THAT ALL 4 FLT ATTENDANTS AGREED AS WELL AS A NUMBER OF PAX. THE SMELL WAS IN THE BACK AROUND ROW 22. EVEN THOUGH THERE WAS NO SMOKE; WE DECIDED THE WISEST ALTERNATIVE WOULD BE TO GET THE AIRPLANE ON THE GND. ZZZ WAS ABOUT 100 MI OFF THE NOSE AND WE WERE AT FL350. SINCE I COULDN'T BE SURE THAT A BURNT SMELL WOULDN'T ESCALATE INTO SMOKE; I DECIDED TO DECLARE AN EMER; HAVE EQUIP STANDING BY; AND PLAN A PRECAUTIONARY LNDG. I IMMEDIATELY NOTIFIED DISPATCH. WE ALSO REVIEWED ANY APPLICABLE CHKLISTS. WE DID A CABIN ADVISORY AND LANDED VISUALLY. I HAD THE FIRE DEPT INSPECT THE OUTSIDE OF THE ACFT AND LATER THE INSIDE AT THE GATE. MAINT REPLACED A HOT AIR VALVE AND WE DISPATCHED TO ZZZ2. I FEEL THE CREW USED GOOD CRM COM SKILLS. WE WERE WELL INFORMED AND FEEL THAT THE FLT ATTENDANTS ARE A VALUABLE TOOL IN RECOGNIZING ABNORMALITIES. WE ARRIVED 3 HRS LATE INTO ZZZ2; HOWEVER; RECEIVED NUMEROUS COMPLIMENTS FROM THE PAX.

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.