Date: 201310
Local time of day: 0001-0600
Location: ZZZZ.Airport, FO
Light: Dawn
Aircraft: Widebody Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Parked
ATC / advisory: Ramp ZZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Physiological - Other; Confusion
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Critical; 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 Crew
When detected: Pre-flight
Result: Flight Crew Became Reoriented; Flight Crew Took Evasive Action; General Physical Injury / Incapacitation
Contributing factors: Company Policy; Aircraft; Environment - Non Weather Related; Human Factors
Primary problem: Ambiguous

Narrative: Aircraft was dispatched an inoperable APU. Our crew arrived at the aircraft for a scheduled departure around dawn. The aircraft was already fueled and loaded. I noticed that while the main cargo door and L2 door were opened when we arrived; the loading appeared complete. The load was mostly food with some pallets containing dry ice. The aircraft was quite cold since no packs were running due to the lack of APU; and no air conditioning carts were present. After we obtained air start carts and completed all preflight preparation; the aircraft doors were closed and one engine was started. About that time we realized that it was getting really hard to breathe - as if we were exerting ourselves hard while in reality we were all sitting in our seats. An increasing level of mental confusion was also present - but that is only noticeable in retrospect. Our Operations Agent/Central Load Planning Coordinator was barely able to return from the main deck after closing the L1 door; and was getting very confused. We were all suffering from hypoxia due to increasing carbon dioxide content in the air inside the aircraft. We quickly turned on two packs and went on oxygen for a bit. That cleared all the ill effects.It was a close call - if we had not realized what was happening and acted on it; all the occupants of the aircraft would have likely lost consciousness and suffocated. By the time the ground crew would have realized that something was wrong; brought the stairs back; opened the door; then alerted Fire and Rescue services; the aircraft would have contained 6 corpses. I note that per our Flight Operations Manual states: 'For widebody transport aircraft on the ground for more than one hour; when carrying more than 440 LBS of dry ice in any compartment; one air conditioning pack should be on'. That is rather hard to comply with if the aircraft has an inoperable APU. Per our NOTOC we had over 10;000 LBS of dry ice on board. I question the legality of operating the aircraft with so much dry ice and no APU. Even more so; I question the wisdom of such operation.


Second narrative: [Reporter narrative added no additional information].


Synopsis: Air carrier crew became hypoxic during preflight because 10;000 LBS of dry ice was loaded on the aircraft; but ventilation was poor because the APU was inoperative while air start carts were being used for ventilation.