Date: 201505
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class A ZZZ
Aircraft component: Pneumatic System
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Diverted; Flight Crew Landed As Precaution; General Maintenance Action
Contributing factors: Aircraft; Procedure
Primary problem: Aircraft

Narrative: During the preflight preparation I started the APU and after confirming the external PC air was disconnected; I asked the First Officer (FO) to turn on the APU bleed for pack cooling. As I looked up at the pneumatic panel both engine bleed air switches were off and I asked the FO to turn them back ON. He said he had not turned them OFF to begin with. This small fact will come into play later to possibly identify the source of our odor.During the takeoff roll and very close to 100 knots I noticed a moderate smell that can be described as rubber/plastic-like; with NO smoke; fire; or fumes present. It was an odor. I continued the takeoff and once established in the climb; the odor began to definitely and positively dissipate in the cockpit (the FO and I discussed the odor after I engaged the autopilot around 2;500 feet) as we climbed and was no longer present above 10;000 feet. Since I had the Flight Attendants seated for takeoff due to possible chop in the climb; after passing 10;000 feet; I asked the FO to let them up and to ask them about any possible odor in the cabin. The Flight Attendant (FA) reported that there was a slight odor detected around the exit rows and the FA's indicated that they would check the rest on the plane. I was monitoring some of this communication on the flight interphone even though I was the Pilot Flying (PF). The FO and I began a discussion about what was developing; our concerns and what we should do. After several calls between the FO and FA's; it seemed the odor was becoming a bit more pronounced; but the FA's were NOT uncomfortable and didn't think it was an issue. The FO asked for continued updates regarding the situation.We had received a clearance above FL230 when I asked the FO to send an ACARS to Dispatch. WE NEVER GOT A REPLY. I saw [a nearby airport] on the Navigational Display (ND) (circled FMC airport) at about 50 NM and getting closer. Before we could call Dispatch via phone patch and climbing through about FL290; the FO was again talking to the FA's on the interphone. I heard the FA from the back of the aircraft state that after opening the aft lavatory door; the rubber-like odor was 'piercing' and that they were getting sick to their stomachs; had headaches; difficulty breathing; burning eyes and burning noses. There was no fire or smoke present. (We later found out that the back few rows of passengers noted it as well)I looked at the FO and we both said almost simultaneously that we needed to divert. I told him that I had the aircraft and ATC and to set me up for a divert to [the] nearest suitable airport; [Another airport] was too far at this point. I asked ATC how long the runway was and I believe they stated the runway was 6;600 feet long. I asked the FO to send a free text ACARS message to Dispatch telling them of our [situation]; BUT NEVER RECEIVED A RESPONSE. (We were an aircraft [in a situation] and attempted to contact Dispatch per the FOM. After no reply I exercised my command authority and handled the [situation] without them).The FO also pulled out the QRH and looked for an appropriate checklist. We determined that the 'Fire; smoke; fumes' memory items did not apply since there was nothing perceptible in the cockpit. There was no smoke; fire or fumes. The FO did a great job and consulted the checklist to see if there was anything contained in the checklist to help isolate a potential problem source. At this point (we were almost on top of the airport and still needing to descend lower) we deemed it more important to concentrate on flying the aircraft and prepping for landing and not isolating systems on a checklist.The FO sent for ACARS landing data; but since that was going to take too long; I asked him to compute the data. We determined even at about our current weight; which was about 7;000 pounds over max landing weight; that our required landing distance would be about 4;600 feet with Flaps 40 and Max Autobrakes. (This included the 15% margin which we knew we didn't technically need in our situation)The weather was completely clear and we were visual from FL290 all the way to touchdown. During this time we continued to set up for the divert; did the TEST brief with the FA's with no evacuation planned unless we decided to do so mutually after landing. We also quick briefed the visual; both confirmed landing distance again for Flaps 40 and Autobrakes Max. We completed the Approach Descent Checklist.At some point I made a PA to the passengers; quickly telling them about the nature of the issue; our diversion and that the situation was under control.We continued to descend to 6;000 feet and ATC vectored us to the West of the airport and on a left downwind and base for the ILS at 2;000 feet. ATC asked for the Souls on Board (SOB) and Fuel on Board (FOB). On our final vector to final and once established I asked the FO if he thought we missed anything important. He replied that he thought everything was complete. (I felt as though we acted promptly; accomplished all tasks; yet did not create an unmanageable situation by proceeding at a faster pace).I transitioned to 1 dot below the glide slope below 200 feet and made a normal touchdown and let the Autobrakes engage in Max. We cleared the runway and the FO made a 'remain seated; remain seated' PA. We then joined taxiway 'Uniform' where Airport Rescue and Fire Fighting (ARFF) met our aircraft. They performed their external check of the aircraft; said our brakes were warm but well below limits and then cleared the area. We then proceeded to the gate after talking to the FAs and getting taxi clearance. We completed all checklists at the gate and wrote up the odor and overweight landing in the logbook. My FO attended to the FAs and I began to coordinate with the station; local maintenance and ARFF. The station was doing a great job with the passengers.After I made several phone calls; my FO who was doing an outstanding job attending to our Flight Attendants and other recovery duties; advised me that 2 of the Flight Attendants were attended to by the paramedics and were given supplemental oxygen due to the burning sensation in their lungs; headaches and nausea.At a later point the entire crew gathered in the first class cabin and I helped lead an informal interactive crew debriefing and support conversation.We also learned from the Duty Manager after his second call; that last night; there was an engine wash performed on our aircraft which uses very toxic chemicals. The engine bleed switch position that we discovered from our preflight was a clue that maintenance must have done some work on the aircraft prior to our arrival. (Refer to the NOTE at the top of this report)The Duty Manager also wanted to administer a Human Factors Assessment for myself and the FO; but after having already consulted with the FO; we had already determined that we were no longer able to fly any further flights. The Duty Manager was supportive of our decision and said the Human Factors Assessment was therefore not required.


Second narrative: Late in the takeoff roll (approximately 100 knots) I began to notice an unusual smell. It was not a familiar odor but somewhat resembled burning rubber or plastic but there was no smoke or fumes. The odor was not terribly strong and I even wondered if it originated from the environment outside the aircraft (i.e. fertilizer etc.) During climb out and at a safe altitude I commented about the smell to the Captain and he too noticed it.


Synopsis: B737 flight crew detects a faint burnt rubber smell during takeoff and continues to 10;000 feet as the smell gradually diminishes. The flight attendants report the odor is also in the cabin but not strong. Later the flight attendants report the odor is very strong in one of the aft lavatories and the crew elects to divert to the nearest suitable airport.