Date: 201911
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Physiological - Other; Workload
Second reporter function: Pilot Flying; First Officer
Anomaly: Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I was [Captain] PM on Aircraft X from ZZZ to ZZZ1. Uneventful pushback; engine start; taxi and takeoff from XXR at ZZZ. On initial climb-out; I smelled a very faint odor in the flight deck. It smelled sweet; and I didn't think much of it at the time because I've smelled plenty of strange odors before and just assumed it was something galley or lav-related. As we continued the climb; the smell became a little bit stronger. It smelled almost exactly like Play-Doh. I asked my (First Officer) if he could smell something and he said no. To see if I was just imagining things; I put on my oxygen mask with 100% oxygen flow selected; and breathed with it for approximately 5 minutes. I no longer smelled the odor. Upon removing my mask; I immediately smelled the odor again. A few minutes later; we reached our cruise altitude of FL350. We completed our cruise duties. I could still smell the odor; and within a few more minutes; my eyes began to feel slightly irritated. The (First Officer/PF) reported that he could smell a faint odor; but reported no physiological effects from its exposure. To get a third opinion; we called the cabin and asked if the Flight Attendants could set up a barrier and if our #1 could come up front to see if he smelled something strange. Upon entering the flight deck; our #1 immediately reported a strong 'sweet' smell and a feeling of 'heaviness' in the air that was not present anywhere in the cabin. After leaving the flight deck; he walked to the aft galley and back to the forward galley and confirmed that the smell was only present in the flight deck. By this time; the 'Play-Doh' odor was a bit stronger; the (First Officer) began coughing; and we agreed that we were experiencing a fume event. We both donned our oxygen masks with 100% flow selected. We [notified ATC] with Center and told them we would be diverting to ZZZ2; which was almost immediately due south of us and within 60 miles. They cleared us to ZZZ2 via direct and we began our descent. The (First Officer) flew the aircraft and took the radios while I ran the QRC for fumes in the flight deck; which directed me to the QRH (chapter) to continue the procedure. I was extremely task-saturated nearly the entire remainder of the flight because the (First Officer) did not have any free hands to do anything but fly the aircraft (he was descending with full speed brakes and coordinating with ATC); so I also programmed ZZZ2 into the box as our new destination; got the ATIS; set landing field elevation; and then built the approach for Runway X. I set the inbound course and frequency for both me (Captain PM) and the (First Officer PF). He handed me his iPad so I could pull up the approach plate for him. I did so; and also gave him a quick briefing on the pertinent items for the approach. I ran the Descent and Before Landing Checklists. While completing these tasks; I was also running QRH for fumes in the flight deck. Step [XX] of the QRH procedure (as well as common sense) directed us to not delay landing in an attempt to complete all of the checklist items; so we prioritized landing at ZZZ2 ASAP over completing the entire checklist. Our masks began to fog up; so we switched to Forced Flow 100% (they cleared up quickly). I called the Flight Attendants as instructed by the QRH procedure to notify them that cabin lighting would be extinguished; but that passengers would have reading lights available. Communication was challenging; as the masks allowed us to talk to only one person at a time (i.e.; if I wanted to talk to the FAs; I couldn't communicate with the (First Officer; PF) while doing so because the mask muffled my voice); which made proper CRM absolutely crucial so that nobody was left out of the loop. The irritation in my eyes was no longer an issue (it only happened when I had my mask off) but my First Officer reported chest pains and painful breathing; even with the mask on. I asked if he felt okay to land the aircraft; and he said he was; but I stayed alert and ready to assume control should he become incapacitated. As we would be landing 6;000 pounds overweight; I also ran the QRH procedure for an overweight landing. ZZZ2 approach vectored us for a visual approach and landing on Runway X; which was conducted without incident. The timespan from initiating the diversion at FL350 to touchdown at ZZZ2 was 20 minutes. My (First Officer) touched down smoothly in the touchdown zone and on centerline. We exited right and stopped the aircraft to ensure the situation was under control and that we were safe to taxi to the gate. After agreeing that we could taxi in without further incident; we notified ATC that it was safe to release the emergency vehicles; and taxied to the gate & deplaned the passengers. None of the passengers or Flight Attendants reported any adverse physiological effects from the fume event; although our #1 said that after landing; they could also smell the odor in the cabin as the aircraft depressurized and the fumes were sucked aft to the outflow valve. After contacting the company; Maintenance and Dispatch; we were sent to a hotel; and from there the (First Officer) and I immediately went to the ER; where we were treated for our respective symptoms we reported during the fume event. After 4 hours of observation; we were deemed to be medically OK and released from the ER.


Second narrative: While leveling off at 35000 from ZZZ to ZZZ1 the (Captain; PM) and I (First Officer) began smelling a very strong odor in the cockpit. After checking the air-conditioning and trying to figure out where the smell was coming from the (Captain) started getting irritated red eyes. Once this occurred we started the checklist for Smoke; Fire or Fumes. As the flying pilot I asked the (Captain) to start the checklist while I spoke with the #1 Flight Attendant to see if the smell was also in the cabin. The smell was contained only to the cockpit. Once I determined this I notified Company Dispatch of our problem. Dispatch responded with a diversion to either ZZZ2 or ZZZ. I elected to go to ZZZ being the closest airport at our 1:00 position. I then [notified] ATC and we both donned our oxygen masks for the duration of the flight. I then joined the (Captain) on the QRC; QRH procedures. With the QRH checklist complete we then started prepping for the Visual approach to runway X into ZZZ2. We printed the weather; discussed and set up the approach; and programmed the FMS for the approach. Being vectored for the descent and slowing for the approach I then called for the Overweight Landing checklist since we were going to land at 152;000 pounds. We set up for this by referencing the QRH; landing with flaps 30 selecting runway 08 as the longest runway for landing. The approach and landing was done with a slow descent rate and as flat as I could and within the touchdown zone of the runway. We then exited the runway at [taxiway] and entered [taxiway] pointing East. We stopped the aircraft to assess the situation and decided to call off the ARFF [Aircraft Rescue & Fire Fighting] equipment. We opened the cockpit windows and took our O2 masks off to continue taxiing to spot L for gate XX where we shut down. After shutting down we realized that during the QRH procedure for the Smoke; Fire or Fumes we isolated and shut down all lighting in the cabin; resulting in the flight attendants using flashlights to assist in deplaning the passengers which went very smooth. I then completed the aircraft logbook with an ODOR entry and an OVER Weight Landing entry. I called Dispatch and my Chief Pilot on call to inform them of the situation. My final call was to MedAir to see what they wanted myself and the (Captain) to do. We arranged a hotel for the crew and headed to the hospital to be assessed. I received a breathing treatment; steroid; and chest Xray; while the First Officer received eye drops. After being monitored for 4 hours in the ER we were released to return to our hotel for rest. We have no idea where the smell came from; while doing the checklist the smell continued after all the isolating we did.


Synopsis: B737-800 flight crew reported a fume event in the cockpit which resulted in a diversion.