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24 April 2015

The suprising chemicals that may be in your emergency oxygen system

A recent article in described a reality that may surprise some passengers. In short, the passenger emergency oxygen system used in some airliners may generate small amounts of toxic chemicals in addition to oxygen. While that may sound a bit scary, the risks to passenger is rather low.

Two types of systems
Passenger emergency oxygen systems provide oxygen from either a centralized oxygen supply system that supplies the oxygen to every passenger, or it is supplied by a chemical oxygen generator that provides oxygen for a small number of masks. Depending on the generator, it may contain a combination of chemicals, which may include sodium chlorate, potassium perchlorate, barium peroxide, or iron powder, that when activated give off oxygen as a byproduct of a chemical reaction.

Chemical oxygen generator hazards
The greatest risks from chemical oxygen generators is the heat that they may generate. However, airliners are designed to take this into account. The other basic risk is exposure to some of the byproducts from the chemical reaction. While the oxygen is filtered before reaching a passenger, is it possible that the trace amounts of chemical byproducts that remain may affect a passenger.

Hypoxia basics
Hypoxia is a condition where the human body is deprived of sufficient oxygen needed for normal bodily function. Hypoxia affects the central nervous system, and those effects may range from impaired judgment and decision making capability, to unconsciousness and death. In an aircraft that has lost cabin pressure while flying at high altitudes, the easiest way to prevent hypoxia is to breathe oxygen from the emergency oxygen system until the aircraft can descend to a lower altitude.

More on hypoxia
You can find an overview of hypoxia risks on If you are interested in the effects of hypoxia on pilots and passengers, you may want to check out this hypoxia overview from the FAA.

Resources article about the chemicals in aircraft emergency oxygen systems
Hypoxia overview
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03 April 2015

Are people with a history of depression or suicide attempts allowed to fly? - Yes they are!

The unfolding investigation of March 2015 crash of Germanwings flight 9525 has revealed that it is very likely that the first officer locked the captain out of the cockpit, and proceeded to deliberately crash the aircraft into the French Alps. Reports by French and German authorities, as well as by Lufthansa, the parent organization of Germanwings, suggest that not only did the first officer have a history of depression, but that Lufthansa was aware of the first officer's condition. Reportedly, German investigators stated that the first officer had been recently treated for suicidal tendencies, but it was not clear if Lufthansa or Germanwings were aware of those recent treatments.

One basic question that many air travelers have is how can anyone with a documented mental illness have become a pilot for a major airline. While the answer in the case of the Germanwings crash may not be revealed until the investigation is complete, it is possible to address that question for US airlines.

The role of medical certificates
In the US, in order to fly, a person holding an airline transport pilot (ATP) certificate, which is the type of certification that any US airline pilot must have, must possess an FAA medical certificate. The specific regulatory requirements regarding mental conditions for those holding an ATP certificate holder are spelled out in the US Code of Federal Regulations (Title 14, Part 67.107). The FAA allows physicians with specialized training to be an Aviation Medical Examiner (AME), who is responsible for evaluating a pilots medical fitness. If a pilot does not pass the examination, that pilot is not legally allowed to fly.

FAA Guide for Aviation Medical Examiners
The FAA provides AMEs with detailed guidance in a number of ways, including publications like the 2015 Guide for Aviation Medical Examiners, which had an update on 19 March 2015, just five days before the Germanwings crash. The document clearly states that a pilot has to respond to a detailed medical questionnaire, and must reveal a history of mental disorders, including depression or suicide attempts. While such a revelation would lead to further investigation, it would not automatically lead to a denial of a medical certificate.

The pilot who is suspected to have deliberately crashed Germanwings flight 9525 conducted part of his airline flight training in the United States several years ago, and would have been subject to FAA regulations during that period.

What do the airlines do?
While it is clear that the FAA allows people with a history of depression or suicide attempts to fly, it is unclear what the policy of individual airlines may be with regards to a pilot with this kind of medical history. What and airline knows about a pilot's medical history will depend on what that pilot would voluntarily reveal, as well as what the airline may legally be allowed to know. Because this would largely depend on where that airline is located, it is possible that what an airline in one country can know about their pilot's medical history may be radically different from what an airline in another country may know.

Resources FAA medical certificate questions and answers
Germanwings flight 9525 crash information
Lufthansa plane crashes
Other A320 crashes
Germanwings Wikipedia page
Flight 9525 Wikipedia entry