The new rule has just been made public by the FAA after a long delay. It was communicated to airlines previous to this date and it has already been made effective in 6000 airplanes across the US commercial fleet as of Friday, March 4. But neither the government nor any of these airlines have notified passengers about these changes.
According to an official FAA note, it and "other federal agencies" (TSA anyone?) think oxygen generators in lavatories are a "security risk". According to these agencies, terrorists may try to use this equipment to take aeroplanes down, turning the oxygen canisters into explosive devices.
The [FAA]ecently required the nation's airlines to disable the oxygen generators located in all aircraft lavatories to eliminate a potential safety and security vulnerability. [...]The FAA, along with other federal agencies, identified and validated the potential threat, then devised a solution that could be completed quickly.
Perhaps more problematic is the fact that, according to this report, the FAA has been trying to tip toe over this issue. The entry was absent from the FAA's website because, according to them, "they wanted to make the changes before the wrong people realised a potential vulnerability".
By taking out the generators, passengers who are in a lavatory during a rapid decompression event will not be able to use the oxygen masks. They will have to run out of the lavatory - in the middle of a confusing emergency situation - back to their seats. They could potentially get assistance from a member of the crew, but who knows what would be the status of the crew during such an event. Michael Cunningham, a Gizmodo reader who experienced a rapid decompression event on Soutwest Airlines Flight 2294, tells how hard this is:
I was on Southwest 2294 when it decompressed. Going from a slight nap to tunnel vision in 7 seconds sucks. I'd hate to imagine what it would be like if my pants were also around my ankles in the process.
The result is that passenger could die or experience lung trauma. I consulted aeroplane pilots and air crew members, and they confirmed that even while they could take the aeroplane down to a safe altitude, the death or trauma risk is very real.
Rapid decompression is a serious risk
In the same note, Lynn Lunsford - Mid-States Communications Manager Federal Aviation Administration - says that you shouldn't worry about this new measure, because rapid decompression events are "extremely rare":
Rapid decompression events on commercial aircraft are extremely rare. If there is a sudden loss of cabin pressure, pilots are already trained to guide the aircraft to a safe, breathable altitude as quickly as possible. Flight attendants are also already trained to assist passengers to quickly access oxygen—including those in the lavatories.
But that's not really true: According to industry experts, decompression incidents are not uncommon on both civilian or military aircraft. In fact, about 40 to 50 rapid decompression accidents occur every year throughout the world, according to a report (PDF) by the Aviation Medical Society of Australia and New Zealand.
So yes, while there are almost no explosive decompression events - like the 1985 Japan Airlines Flight 123 that killed 520 people in a 747 - rapid decompressions events do happen. The most recent notorious case was in October 2010, when an American Airline's Boeing 757 flying from Miami to Boston had a 0.6m hole open in its fuselage at 31,000 feet. With little oxygen at that altitude, 154 passengers and crew had to use their masks while the plane returned to Miami Dade International Airport.
• Explosive decompression happens in less than 0.1 to 0.5 seconds and its effects are similar to a bomb detonation. Trauma risk is very high in the respiratory system. Oxygen masks deploy.
• Rapid decompression takes more than 0.1 to 0.5 seconds. Lung trauma risk still exists. Oxygen masks deploy.
• Slow decompression happens gradually and may not be detected by the crew, instrumentation or the passengers. This could be very dangerous, as it may cause hypoxia that could make the crew to pass out without detection.
The year before that, Soutwest Airlines Flight 2294 suffered a similar rapid decompression incident. The 126 passengers and five crew members were making excellent use of the oxygen masks in their Boeing 737-300 before landing at Yeager Airport in Charleston, West Virginia.
This is exactly why there are oxygen masks in airplanes in the first place. If these incidents were so "extremely rare" and could be handled by the crew so easily, the FAA would not mandate aircraft manufacturers to install oxygen masks anywhere in the plane. It was thanks to the masks that all the passengers were perfectly fine. Without the masks, they may have died or experienced lung trauma.
From now on, if you are in the lavatory, that may be your fate.