Date: 202012
Local time of day: 1801-2400
Location: ZZZ.TRACON, US
Flight conditions: Mixed
Weather elements / visibility: Rain; Windshear
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Reporter function: First Officer
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Time Pressure; Fatigue; Workload
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant; Person Flight Crew
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition; Flight Crew Diverted; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: The Captain gave me the plane and started making calls on COM2 which I did not listen in on. Operations attempted a Dispatch patch which didn't work; Dispatch via airnav; Flight attendant calls; and PAs. Meanwhile I was flying the plane with automation; getting vectors from ATC; descending (I believe we were around 30;000' when we decided to divert); and fielding ATC questions to a limited extent. We were able to go and stay VMC at some point during this time although it was night.Maybe 6 minutes later the Captain was back with me and he took the airplane. At that point I started working the box with a bit of help from the Captain. I was still also handling most of the ATC calls at that point. We ended up getting direct to a waypoint that put us on a base to final for Runway XXL. Shortly thereafter they changed it to Runway XXR. Unfortunately I wasn't able to send for the numbers until we were turning final. I ran what I could of the descent checklist as I waited for them to come back. As they finally came up; Captain said it was too late; he would use green dot as a reference for landing. I expressed that I was OK with that and pulled myself away from the automation. Either shortly before or after this the Captain commented a different strange smell in the cockpit; I verbalized smelling it as well but am unable to describe it accurately- maybe some kind of fumes. Remember at this point we had a real concern that there was a fire with a fuel leak despite the lack of alarms or EICAS msgs.The Captain executed a very nice landing and I continued to communicate with tower on the dedicated frequency. We pulled off and came to a stop. Captain asked for a fire truck to inspect the plane which was accomplished without any abnormalities or fire indications found. We then proceeded to gate in the company ramp. At some point during this latter taxi the smell dissipated from the cockpit. I suggested not turning the APU on as it could have been the source of our issues. Captain agreed and asked me to notify Ops that we wanted to taxi in and leave engine 1 on while they hooked up the ground power. I relayed this and it took a while but was eventually accomplished. We shut down and medics came into the forward doorway asking to assess/treat folks. The flight attendants seemed to be the only ones reporting headaches/symptoms from the incident; especially FA2. Both FA2 and FA3 did a great job throughout the situation. I was especially impressed with FA2 doing her job professionally while in obvious distress after the cockpit door was opened. The medics basically had to insist on taking her for evaluation while the Captain stepped in to the forward cabin and volunteered to perform any of her FA duties necessary while the passengers deplaned. I remained in the cockpit monitoring the systems.Captain demonstrated superb leadership and decision making skills this night and I feel very lucky to have been working with him during this event.We talked to a variety of ground personnel and mechanics after a quick debrief. One mechanic firmly believed that de-ice fluid was ingested in the APU and that caused the odor. Captain and I were skeptical as we had not de iced all day and had been in heavy rain. The mechanic showed me the aft of the aircraft and there did indeed appear to be a small streak of fluid (not water) on the belly forward of the APU inlet. However to me it looked like the fluid came from the APU as the fluid was more concentrated there and disappeared as the streak moved forward on the small belly fin for maybe 8'. I took a few photos which should be attached. It's also noteworthy that we had this same aircraft for the last 2 flights (about 4.5 flight hrs) which included an identical takeoff from ZZZ.Unfortunately it took over an hour for everyone; especially the FAs; to complete all the required phone calls and documentation. We were unlucky enough to wait over 45 minutes for ground transportation during which we talked to crewscheduling and the contacted the shuttle company multiple times. We all got to the hotel after X pm truly exhausted from the experience and without an opportunity to get any dinner. Surprisingly I wasn't the only crew member to mention trouble sleeping as I unwillingly replayed the events over and over in my mind. In hindsight now it's interesting to evaluate myself going from the adrenaline spike during the incident; to the fatigue crash afterwards; to the inability to relax when I finally got to the hotel room. The following day which was supposed to be my day off was a deadhead home. That afternoon I evaluated my condition and thought it appropriate to ask for a later start for my next 3 day trip starting the following day. I will evaluate myself again on the next day and ask for yet a later time/day to join this next trip if necessary.Despite all the great training I've had to it was a valuable experience to go through this in real time. It was interesting as this evolved from a transient cockpit odor to a de facto emergency landing. We do get mild transient odors in the cockpit from time to time without consequence and I really thought this would be a similar outcome. I fully expected the flight attendants to report the odor gone as we continued the climb out and found myself a bit surprised to be going into ZZZ2 even though we literally had just been discussing it before the decision was made. After extensive reflection I feel like we handled the situation very well. I do think in hindsight that we could have communicated even more during that extremely busy descent. We both debriefed about looking at the landing weight during the descent; thinking it was okay; and deciding it better to land even if we were slightly over weight anyway but I don't remember either of us verbalizing it in flight. We also didn't discuss our obvious decision not to hold and run checklists which we both decided was not the best option. There is an argument to be made that it we had our hands full safely getting the plane down ASAP and those discussions were OK to save until later. In hindsight we probably should have [communicated the urgency to ATC] at some point. Initially the Captain and I had some uncertainty as to how strong the fuel smell was in the aft cabin but decided it was time to go to ZZZ2 regardless. As soon as we described the situation to ATC they treated it as an emergency and we were busy enough not to discuss or bother officially declaring it.




Synopsis: EMB-175 First officer reported a fumes event during initial climb resulting in a diversion.