B737 flight crew reported a fume event during preflight after the packs were turned on and the deplaning of the aircraft was subsequently performed orderly and safely. The aircraft was inspected and the flight crew was removed from the flight for medical reasons.
Synopsis
B737 flight crew reported a fume event during preflight after the packs were turned on and the deplaning of the aircraft was subsequently performed orderly and safely. The aircraft was inspected and the flight crew was removed from the flight for medical reasons.
Narrative
At approximately XA:40; the APU was started as boarding was complete. Approximately XA:50 the APU was connected to the electrical system and the APU bleed and packs were turned on. About 30 seconds after the packs were turned on; the First Officer (FO) mentioned seeing what was described as a haze on the left side of the cockpit. About the time FO mentioned the haze; I picked up the smell of something hot and then smelled smoke. I quickly stood up in the cockpit to get a good view of the cabin. At that time I saw smoke accumulating at the ceiling from the front of the airplane all the way to the back. I then told the Purser to make a deplane announcement to the passengers. As I was telling the Purser to deplane; the aft flight attendants called the Purser to tell her they were seeing smoke in the cabin. I then went back into the cockpit and immediately shutoff the APU bleed switch and the pack switches. After I shut off the switches; I made an announcement over the PA to reinforce the Purser's announcement for the passengers to leave their belongings and quickly deplane. I had the FO contact Operations and Maintenance to inform them of what was going on.When Maintenance arrived; they made mention that the odor smelled electrical. The deplaning of the aircraft was performed orderly and safely with the passengers cooperating with the instructions that had been given. The aircraft was quickly emptied and the ZZZ Fire and Rescue arrived to make sure there was no fire. Upon entering the cabin; the firefighters mentioned the odor smelled like something electrical. The firefighters then performed an inspection of the E&E compartment; cockpit; and exterior and could not locate a fire or source of the smoke. After we received an all clear from Airport Rescue and Firefighting (ARFF); the APU was shut down and ground power was reconnected to the aircraft. The passengers were then brought back onto the aircraft in groups of approximately 5 at a time to retrieve their belongings. After this process started; I went up into the terminal and made a call to the Chief Pilot to inform him of what was going on. This process took approximately 30 - 60 minutes to complete.After all the passengers' belongings were retrieved; I gathered all the crew into Operations for a debrief to assess how everyone was doing. The majority of the crew had some degree of headache; a couple were experiencing some minor breathing difficulties; and a couple described a minor brain fog-like symptom. I then reached out to my local union rep who offered no suggestions or help with the situation. I called back to the Chief Pilot and told them the whole crew would be going to the emergency room for evaluation. A ZZZ Operation Representative drove me and the other 5 crew members to the emergency room. Upon check-in; we were told it would be a 4-hour wait. The nurses in the ER clearly saw the 6 of us in uniform and went out of their way to prioritize us over those that were waiting. All 6 crew members were found to have elevated carbon monoxide levels with the cockpit crew having the highest. The crew was discharged and we returned to the airport to gather our bags and to head to the hotel. Enroute to the airport; I called the Chief Pilot and briefed her on the status of the crew. I told her that the cockpit crew were found to have above normal carbon monoxide levels and the decision was made by her to have us removed from the remainder of the trip and sent home to have corporate medical follow up later in the week.
Second reporter narrative
At about XA:45 local time; when passengers were almost completely boarded; the APU was started. Shortly thereafter it was placed on the electrical bus; and three or four minutes later I switched on the left and right packs; made sure the isolation valve switch was in the open position; then turned on the APU bleed. I then resumed other preflight duties. I would guess about 30 seconds later; I heard the Captain (CA) say; 'I smell something burning.' I immediately looked at the CA and noticed a smoky haze. I verbalized this and the CA turned to look back into the cabin and saw smoke throughout; particularly along the ceiling. The CA told the Purser to quickly evacuate the aircraft back up the jetbridge into the airport. The Purser made an announcement that was reinforced shortly after by an announcement from the CA. One of us reached up and turned off the APU bleed and packs and it seemed the smoke stopped. Once the passengers deplaned - in an organized manner; leaving their bags onboard - Maintenance arrived; then the Airport Fire and Rescue. No breakers were found popped; though members from both entities made comments that the smoke smelled 'electrical' or like 'electrical wire insulation burning;' matching what the CA and I thought. No fire was discovered on the flight deck or the E&E compartment.A smoky haze remained throughout the aircraft. After the fire and rescue personnel left; Maintenance ran a few checks; and did make comments that 'it could just be a little burning oil;' contradicting their earlier comments about an electrical smell. It felt as though we were being told the aircraft was ready to fly. The CA officially denied the aircraft at that point. The flight attendants reentered the aircraft and passengers were allowed to return one row at a time to collect their possessions. After this process; the crew convened in the local Operations office to debrief. All six of us had headaches; some had shortness of breath and/or 'brain fog.' The CA made many phone calls to the Chief Pilot; company; and the union; and no one offered assistance or advice. We decided as a crew that a precautionary hospital visit was prudent. A ZZZ Operations employee drove us to the emergency room where we were treated very well. The CA and I were found to have the highest levels of carboxyhemoglobin from carbon monoxide exposure; both above the normal range. We returned to the airport to grab our bags; then made our way to the hotel. On the way to the hotel; the CA called the Chief Pilot; who upon hearing about our hospital results; removed the CA and I from the remainder of the trip. As far as I know; no passengers sought medical care.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.