Date: 202102
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
Aircraft component: APU Pneumatic System & Ducting
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor; Ground Event / Encounter Other / Unknown
Detector: Person Flight Attendant; Person Flight Crew
When detected: Aircraft In Service At Gate; Taxi
Result: Flight Crew Returned To Gate; General Evacuated; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I am submitting this copy of a fumes report submitted following a SOF event that occurred following deicing at the gate at ZZZ as a report. The only thing I might add pertaining to legalities is that after the event when we elected to attempt to fly the leg a second time before Maintenance took the plane out of service; that decision was made after conferring with the Duty Chief at Maintenance Control who had consulted with Maintenance following the SOF event. We had been running the packs with the APU for a long period of time after the passengers deplaned; and then did an engine run on top of that to blow out the entire air conditioning system and had no further issue with deicing fumes. The plane was only subsequently removed from service because it came to light that there might be an IOD claim from one or more of the flight attendants (3 of whom elected to deadhead home on the very same airplane they'd been working on when we had the fumes event) 'This is a report of a fume event that occurred post-deicing at the gate at ZZZ. A separate Fume Event form was also submitted. This is the third such occurrence I have encountered following ZZZ deicing in the past 2 years. In the previous 2 occurrences the effects were much less pronounced and not deemed a hazard because their duration was brief and the cause obvious. In those two cases when the aircraft was reconfigured post-deicing; when the packs were reinstated there was an immediate introduction of visible deicing fluid fumes entering the flight deck; with a much less pronounced but slightly noticeable effect in the cabin that did not warrant any action or alarm. In both cases the packs were turned off and cockpit windows opened followed by an eventual attempt to turn the packs back in one at a time with no further issues. In this case the same thing happened only to a much greater and somewhat alarming degree. When we ran the reconfiguration checklist using the HOT app in this event; turning the APU bleed on reinstated the packs which caused an immediate introduction of thick deicing fluid smoke into the flight deck. My memory of the next couple minutes is a blur because it felt like there were several things demanding my attention and not a lot of information to triage their importance and make a proper best decision given all the variables present. The cockpit smoke was so thick that I could barely see the First Officer and had to feel for my oxygen mask to find it. At some point the packs were turned off; oxygen masks used and the cockpit windows opened. At that point my primary concern was how bad did it get in the cabin? Based on past experience and the current magnitude of the problem; I suspected not nearly as bad as the flight deck but probably getting everyone concerned. Almost immediately the flight attendants called and said the cabin was hazy and what was going on? I said it was deicing fluid and tried to ascertain their assessment which while alarmed didn't suggest it was dire. (The QRH was never considered as the smoke/removal procedures are inflight procedures and rely on using the packs). At this point I was weighing the possibility of evacuating into frigid; arctic conditions with high winds onto a glycol-covered ramp (including 2 wheelchair passengers) vs getting the jetbridge up to the aircraft ASAP (as soon as possible) in case an [immediate] deplaning was deemed advisable. I asked the First Officer to contact ramp control to get the jetbridge attached immediately and tried to think of a way to provide some relief to the cabin air situation. I called the flight attendants back and instructed them to disarm all their doors and to the extent possible crack them open a couple inches to get fresh air into the cabin. That turned out to be unsuccessful because a tailwind was blowing the APU fumes from back to front so that idea was abandoned pretty quickly. Based on my previous two experiences I began wondering if enough time had gone by and perhaps turning the packs on might actually help to bring fresh air into the cabin so I experimentally flipped on the left pack only; but the smoke returned and I immediately turned it off again. It felt like a Catch-22 situation. I knew the only way we could clean out the air was to run the packs but I didn't dare turn on the packs again with the passengers on board. The jetbridge was eventually attached during which time I had assessed the cabin personally and there was a faint lingering odor but nothing I considered alarming. After the passengers were off I asked the flight attendants to self-assess whether they were okay to continue or did they want some medical evaluation and they all said yes they could continue. At some point I contacted the Duty Chief Pilot and after he consulted with Maintenance they suggested doing an engine run. It was at this point that the gate agent informed me that the flight attendants; who had also deplaned; that the flight attendants 'did not want to take this airplane'. We eventually did run both engines at the gate; using both APU and engine bleeds to blow out the pack air until we were satisfied that there were no further issues with fumes. At some point 4 standby flight attendants were assigned and we reboarded the aircraft and departed. My strategy this time was to take the APU completely out of the equation and we requested and received permission to deice at the CDF instead. Halfway into this deicing I was notified something to the effect that the previous flight attendant crew was claiming an injury on duty and because of that Maintenance was therefore taking that plane out of service. We eventually returned to the gate and deplaned to a different aircraft. As I reached the new gate boarding area I saw an off duty [Company] pilot [Name] waiting to board and I asked him for a candid assessment of his impression of what the cabin situation seemed like; and he confirmed my initial suppositions; namely that it was noticeable but not alarming. He likened it to the kind of haze that might be initially experienced when turning on the packs in very humid conditions; but nothing like the thick smoke we encountered in the cockpit. Once again we had to deice but the CDF was closed by then; so I modified our post-deicing procedure to turning the pack switches off prior to reinstating the APU bleed; and leaving them off through both engine starts and then turning them on after the APU bleed was off at the conclusion of starting the engines. We finally departed uneventfully.' I believe the cause of the fume event was 'inadvertent introduction of Type 1 deicing fluid into the APU intake'. I have one recommendation that I will personally use from now on; namely what I mentioned earlier which is not running the packs until they are set for engine bleed as the air source following deicing. I also have to wonder why this has happened 3 times now (all at ZZZ). Clearly there needs to be more emphasis on protecting the APU inlet door when spraying Type 1 fluid. I don't know their procedures; but maybe spraying in brief spurts above the inlet door from back-to-front might help; or just avoiding the area altogether and clearing it by hand in the worst case scenario; but I'm picturing the usual visual of Type 1 fluid cascading down the cockpit windows like a car wash; and if that is going on in the back of the fuselage that can't be a good thing.




Synopsis: B737-800 Captain reported a fumes event during gate de-icing; which resulted in a cabin crew replacement due to physiological symptoms.