Airplane Asphyxiation

Could drop-down oxygen masks have saved a dying airline passenger?

What conditions merit the use of oxygen masks in flight?

An airline passenger had difficulty breathing and then died during a flight from Haiti to New York on Sunday. According to a relative on the plane, the crew aboard the Airbus 300-600 tried to administer oxygen from a pair of tanks that were empty. (American Airlines has countered that the passenger did receive oxygen.) If the tanks really were empty, could the pilot have deployed the emergency oxygen masks?

Yes, as a last resort. Under normal circumstances, the emergency oxygen system in the main cabin kicks in automatically when the cabin pressure drops to that of about 14,000 feet above sea level, or what you’d experience if you were standing near the top of Mount Rainier in Washington. Many commercial jets—most of the ones Boeing makes, for instance—give the pilot the ability to engage the masks manually; this comes in handy when it’s time to inspect the equipment. In an Airbus 300 (which is similar to the Airbus 300-600), the pilot can selectively deploy masks in one section of the cabin. Even if a plane lacks the manual capability, though, a pilot can still trigger the system by lowering the pressure of the cabin with a dial. In dire situations, it would be possible for a passenger to jimmy the overhead panel herself to get at the emergency mask. You’d have to use something like a pencil to push just the right spot.

If the oxygen tanks on the flight from Haiti were indeed empty, the drop-down masks might not have saved the passenger. The emergency system is designed to give just enough chemically generated oxygen to prevent healthy people from passing out for about 10 to 15 minutes. (The masks also allow cabin air to mix with the oxygen.) That might be enough time for the plane to descend to an altitude at which passengers can breathe more normally, say at 10,000 feet above sea level. But it may not be enough for someone who’s seriously sick. On the other hand, a passenger who needs more than 15 minutes of oxygen could try switching from one drop-down mask to another. Each begins to release the gas only after the attached lanyard has been pulled. (In some planes, pulling one lanyard will activate all the masks in that row.)

Commercial planes are required to carry portable oxygen tanks that can be used by sick patients in medical emergencies or by flight attendants who need to move around a depressurized cabin to help passengers. (The cylinders, which come in green, tan, or white, are also called “walk-around tanks.”) Each typically contains 15 to 30 minutes’ worth of oxygen; American Airlines says that Sunday’s flight was equipped with 12 such bottles.

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Explainer thanks Richard Fanjoy of Purdue University, Steve Jones of Western Michigan University, and William Waldock of Embry-Riddle Aeronautical University,