Date: 201510
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ramp ZZZ
Aircraft component: APU
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Workload; Communication Breakdown; Time Pressure; Physiological - Other
Second reporter function: Check Pilot; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor; Ground Event / Encounter Other / Unknown
Detector: Person Flight Attendant
When detected: Aircraft In Service At Gate
Result: Flight Crew Took Evasive Action; General Evacuated; General Maintenance Action; General Work Refused
Contributing factors: Procedure; Aircraft; Company Policy; Human Factors; Manuals
Primary problem: Company Policy

Narrative: After getting pushback clearance from ramp control; the lead flight attendant called to report smoke in the cabin visible with a strong odor. The following events happened quickly. I have tried to write them in chronological order to the best of my recollection. I told the push crew to cancel the push and called for the cabin fire smoke QRH. I called the FA (Flight Attendant) back to ask how much smoke there was; to which she replied that there was a haze layer in the back of the cabin. I turned off the packs and APU air to minimize possible smoke sources then turned off the APU. We opened the flight deck windows then the door and confirmed the cabin smoke had stabilized and intensity wasn't increasing so I asked the FAs to disarm the doors. I asked the push crew to ask the gate agent to bring the jet bridge back and also signaled to the gate agent to bring the jet bridge back. The FO (First Officer) called ramp control to let them know we had smoke in the cabin and requested fire department assistance then called operations to inform them and request wheel chairs and an aisle chair. I made an announcement to the passengers that we were aware of the smoke haze in the cabin and asked that everybody get off the airplane through the front cabin door as quickly as possible as a precaution. I asked that they not take personal belongings to expedite the evacuation. I shut off the APU by selecting the fire control switch to OFF AND AGENT ARM. I noticed that the smoke was stagnant so I tried to clear the smoke by closing the outflow valve and right pack to HP bleed off but then realized it could create more smoke so I turned off the pack. The fire department and maintenance personnel boarded the airplane through the aft stair and the smoke cleared. The fire department walked through with a device and confirmed there was no imminent fire danger. The crew did an excellent job communicating observations to me and executing the deplaning process without incident.Prior to the smoke in the cabin report form the FA; the APU had been running for approximately five minutes with the right pack on HP BLD OFF (High Pressure Bleed); APU air on and cross feed levers open in preparation for engine start. The smoke remained over the aft part of the cabin until after the aft stair was opened. There was a previous write up a few days earlier for an APU OIL PRESS LOW indication. After the passengers were safely in the terminal; I notified crew services and duty pilot about the incident and advised that I did not feel safe to fly the scheduled trip and the entire crew was still shaken up about the incident. I stated that I would not be able to focus on the flight and instead would be mentally evaluating the smoke in the cabin incident. Captain called me back and left a voicemail stating that he spoke with [multiple company representatives] who 'were all 100% fully comfortable with us continuing' and that I would need to contact my chief pilot if I still felt that we were not ready to continue. I spoke with [the Chief Pilot] and expressed my concern about not feeling safe to fly so soon after such a serious incident. [The Chief Pilot] supported my decision to not continue the flight. I also received a phone call from crew services asking if I was going to fly or not. I again had to explain that I was not safe to fly. Having been part of a flight crew who had to previously evacuate an entire flight on a taxiway for smoke in the cabin; I take cabin smoke; possible evacuations and the safety of the crew and passengers very seriously. I feel that in this incident with the smoke intensity not increasing; it was safer for the passengers to expeditiously exit through the main cabin door into the gate area. A separate cabin fire/ smoke on the ground QRH procedure would provide better guidance to quickly isolate possible smoke sources such as APU air or cabin light ballasts that have led to evacuations in the past. Many emails have been sent by thesafety department about the evacuation decision making process but these are forgotten and pilots who begin employment after the emails are sent; have no access to the information. QRH procedures remain on the aircraft and are repeatedly reviewed by pilots.I realize now that although opening the flight deck door provided immediate assessment of the smoke in the rear of the cabin; it also added complexity to the situation. Having a flight attendant in the flight deck while trying to manage the situation; complicated matters. Although intercom communication can be difficult; a flight attendant can correctly describe smoke intensity. A closed flight deck door would have allowed better situation awareness and decision making process from the flight deck out. Improved standard maintenance procedures are needed at our carrier. In this case; the correction action on the logbook after the APU oil pressure low write-up was; no oil pressure low indication during normal operation. A standardized checklist could have guided mechanics through minimum steps required before signing a discrepancy off. Steps such as checking oil levels and verifying no evidence of oil leaks present; would have likely prevented this incident. I realize that not every discrepancy can have a maintenance checklist; but each malfunction indication should have a specific guide that's required to be evaluated by mechanics before returning the aircraft to service. I believe that we were moments away from a full evacuation. If the flight attendants would have delayed notification of the smoke and smell; or if we would not have thought of turning off the APU air; a full evacuation was likely imminent. Smoke in the cabin has the potential of incapacitating everyone in the airplane in less than 90 seconds. Therefore; I consider any smoke in an airplane a very dangerous situation where lives are at elevated risk. After significant incidents such as this one; flight crews should be taken off immediate duty assignments in the interest of safety. We must reconsider the list of events from which operations makes the decision to remove pilots from duty after significant incidents. After expressing concern to a duty pilot about not being able to safely continue a flight; a pilot should not have to re-iterate the concern numerous times to several persons. This process of having to re-iterate that one doesn't feel safe; could end in a pilot feeling pressured into flying even after originally expressing concerns.


Second narrative: There was a previous write up in the maintenance logbook for low oil pressure from the APU. Maintenance later said there was visible oil on the ram doors; and this is what potentially caused the smoke in the cabin.


Synopsis: An MD-80; prepared to push back; was evacuated at the gate after the flight attendants reported smoke in the cabin. Maintenance believed the APU was the smoke's source.