Narrative:

Approximately 15 mins after departure I instructed the flight attendants to stay seated due to possible turbulence. I was then told about a 'strange smell in the cabin.' I asked if any smoke was observed and the answer was negative. I asked them to keep me posted. Approximately 30-40 mins into the flight; I called to ask about the smell. The flight attendants informed me the smell was still present and it seemed to be coming from the front half of the cabin. Shortly after; we noticed the unidented odor on the flight deck. It smelled like hot; possibly overheated plastic/rubber/insulation. It was hard to tell if it was electrical or pack/ducting related. The first officer and I agreed to divert the flight to ZZZ as a precaution. We notified ATC about the problem and received clearance to ZZZ. With the information we had at that time; no smoke in the cabin or the cockpit; I elected not to declare an emergency. I made a PA to the customers informing them about the divert and the reason for it. I instructed the flight attendants to secure the cabin and that an evacuate/evacuation was unlikely at this time. I informed dispatch via ACARS about the divert. We complied with and completed the QRH for fumes in the cockpit/cabin. On final approach I requested to stop the aircraft on the runway after landing to get a status/confirmation from the cabin regarding the status of the odor/fumes. Tower approved. The flight attendants reported odor but no smoke. We taxied to gate after a few moments of confusion due to frequency blockage and a lot of coordination issues with tower and the fire chief. I completed the logbook and made the required entries. Preliminary; one of the mechanics informed me he found ruptured ducting in the east&east compartment; but I have limited information for the reason of the unidented odor. Supplemental information from acn 806409: 15 mins into flight we were informed that the flight attendants smelled an odor resembling overheated plastic/rubber. Within 20 mins the odor spread to the back of the aircraft as well as the cockpit. No smoke was evident. After we completed the QRH checklist; we decided to land short of our destination. ZZZ was the closest (120 mi) and we had a tailwind; so we asked for and received clearance to ZZZ. We had an uneventful landing. I learned afterwards that the inbound flight attendants noticed a 'strange smell' on the inbound leg. The off-going pilots made no mention to us; so it's unclr if they knew about the odor. Especially when we're feeling a bit rushed due to the late inbound aircraft; take the time to do a thorough enough pass down with the flight attendants as well as talking to the pilots. Also; if flight attendants noticed something and feel the need to tell the oncoming crew; then they should certainly tell their pilots as well.

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Original NASA ASRS Text

Title: B737 FLT CREW IS INFORMED BY CABIN CREW OF FUMES OR STRANGE ORDER IN CABIN AND ELECTS TO DIVERT TO ZZZ. INBOUND CABIN CREW ALSO REPORTED STRANGE SMELL BUT NO LOGBOOK ENTRY WAS MADE.

Narrative: APPROX 15 MINS AFTER DEP I INSTRUCTED THE FLT ATTENDANTS TO STAY SEATED DUE TO POSSIBLE TURB. I WAS THEN TOLD ABOUT A 'STRANGE SMELL IN THE CABIN.' I ASKED IF ANY SMOKE WAS OBSERVED AND THE ANSWER WAS NEGATIVE. I ASKED THEM TO KEEP ME POSTED. APPROX 30-40 MINS INTO THE FLT; I CALLED TO ASK ABOUT THE SMELL. THE FLT ATTENDANTS INFORMED ME THE SMELL WAS STILL PRESENT AND IT SEEMED TO BE COMING FROM THE FRONT HALF OF THE CABIN. SHORTLY AFTER; WE NOTICED THE UNIDENTED ODOR ON THE FLT DECK. IT SMELLED LIKE HOT; POSSIBLY OVERHEATED PLASTIC/RUBBER/INSULATION. IT WAS HARD TO TELL IF IT WAS ELECTRICAL OR PACK/DUCTING RELATED. THE FO AND I AGREED TO DIVERT THE FLT TO ZZZ AS A PRECAUTION. WE NOTIFIED ATC ABOUT THE PROB AND RECEIVED CLRNC TO ZZZ. WITH THE INFO WE HAD AT THAT TIME; NO SMOKE IN THE CABIN OR THE COCKPIT; I ELECTED NOT TO DECLARE AN EMER. I MADE A PA TO THE CUSTOMERS INFORMING THEM ABOUT THE DIVERT AND THE REASON FOR IT. I INSTRUCTED THE FLT ATTENDANTS TO SECURE THE CABIN AND THAT AN EVAC WAS UNLIKELY AT THIS TIME. I INFORMED DISPATCH VIA ACARS ABOUT THE DIVERT. WE COMPLIED WITH AND COMPLETED THE QRH FOR FUMES IN THE COCKPIT/CABIN. ON FINAL APCH I REQUESTED TO STOP THE ACFT ON THE RWY AFTER LNDG TO GET A STATUS/CONFIRMATION FROM THE CABIN REGARDING THE STATUS OF THE ODOR/FUMES. TWR APPROVED. THE FLT ATTENDANTS RPTED ODOR BUT NO SMOKE. WE TAXIED TO GATE AFTER A FEW MOMENTS OF CONFUSION DUE TO FREQ BLOCKAGE AND A LOT OF COORD ISSUES WITH TWR AND THE FIRE CHIEF. I COMPLETED THE LOGBOOK AND MADE THE REQUIRED ENTRIES. PRELIMINARY; ONE OF THE MECHS INFORMED ME HE FOUND RUPTURED DUCTING IN THE E&E COMPARTMENT; BUT I HAVE LIMITED INFO FOR THE REASON OF THE UNIDENTED ODOR. SUPPLEMENTAL INFO FROM ACN 806409: 15 MINS INTO FLT WE WERE INFORMED THAT THE FLT ATTENDANTS SMELLED AN ODOR RESEMBLING OVERHEATED PLASTIC/RUBBER. WITHIN 20 MINS THE ODOR SPREAD TO THE BACK OF THE ACFT AS WELL AS THE COCKPIT. NO SMOKE WAS EVIDENT. AFTER WE COMPLETED THE QRH CHKLIST; WE DECIDED TO LAND SHORT OF OUR DEST. ZZZ WAS THE CLOSEST (120 MI) AND WE HAD A TAILWIND; SO WE ASKED FOR AND RECEIVED CLRNC TO ZZZ. WE HAD AN UNEVENTFUL LNDG. I LEARNED AFTERWARDS THAT THE INBOUND FLT ATTENDANTS NOTICED A 'STRANGE SMELL' ON THE INBOUND LEG. THE OFF-GOING PLTS MADE NO MENTION TO US; SO IT'S UNCLR IF THEY KNEW ABOUT THE ODOR. ESPECIALLY WHEN WE'RE FEELING A BIT RUSHED DUE TO THE LATE INBOUND ACFT; TAKE THE TIME TO DO A THOROUGH ENOUGH PASS DOWN WITH THE FLT ATTENDANTS AS WELL AS TALKING TO THE PLTS. ALSO; IF FLT ATTENDANTS NOTICED SOMETHING AND FEEL THE NEED TO TELL THE ONCOMING CREW; THEN THEY SHOULD CERTAINLY TELL THEIR PLTS AS WELL.

Data retrieved from NASA's ASRS site as of May 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.