- You know those oxygen masks the flight attendants
promise will drop from the ceiling if your airplane
starts to go down?
Do you ever wonder where all that oxygen comes from?
Is there one big oxygen tank above the luggage compartment
or do I get my own oxygen tank?
It turns out it's neither.
There is no oxygen tank.
And the thing up there that does give you oxygen,
brought a passenger plane down in the Everglades in 1996,
killing all 110 people aboard.
(wind whirling)
In case of emergency,
oxygen masks may drop from the ceiling above you.
Place the mask over your nose and mouth
and breathe normally.
Oxygen will be saved, even if the bag does not inflate.
But,
How?
It doesn't make sense to put a big oxygen tank
on most passenger planes, it would take up a lot of space
and be really heavy to store enough oxygen gas
for all of the passengers on a commercial flight.
But if the cabin depressurizes, while you're up in the sky,
you're gonna need an additional oxygen source
so you don't suffocate.
Above 30,000 feet, there's less than a third
of the available oxygen that there would be
down at sea level.
To keep a ready supply of oxygen without the weight
of a pressurized tank, airlines use these.
This is a chemical oxygen generator.
It's about the size of two stacked soda cans
and it's filled with Sodium Chlorate, Iron Powder,
Barium Peroxide and Potassium Perchlorate.
When you pull your mask firmly towards you
to start the flow of oxygen.
Pull your mask firmly towards you
to start the flow of oxygen.
You're actually releasing a spring loaded striker
that hits a percussive charge.
This tiny explosion starts a chemical reaction
and the Sodium Chlorate begins to decompose
into Sodium Chloride and Oxygen Gas.
The Iron Powder reacts with Oxygen and releases heat,
keeping the decomposition going.
The gas flows out of the generator, down the tubing
and into your mask.
As you take a big breath in,
you might notice a burning smell.
This is totally normal due to the decomposition reaction
above you, but can be understandably distressing
in a plane where things are already clearly going wrong.
And don't be alarmed if the bag doesn't inflate,
it's just there to hold extra oxygen.
So assuming you keep breathing in, you're likely inhaling
all the oxygen before it has a chance
to back up and fill the bag.
The reaction also gives off a little bit of Chlorine Gas,
which is why the Barium Peroxide is there.
Barium Peroxide helps to soak up the Chlorine
that you really don't want to inhale.
Now, the generators are only designed to provide about
12 to 22 minutes worth of breathable oxygen.
The designers assume that if the masks are needed,
the plane is also probably going into
an emergency descent profile.
AKA it's getting back to the ground
as quickly and safely as possible.
So the chemical core is actually cone-shaped,
it's wider at the beginning
when you'll likely need more oxygen
and then smaller at the end, when you've hopefully descended
back down to a safer altitude.
The exothermic reaction keeping you alive,
can reach temperatures above 1000 degrees Fahrenheit.
That sounds kind of frightening.
But it's not the only place where we use
this kind of technology.
In fact, two other confined spaces, submarines
and the International Space Station, both use oxygen candles
to create breathable O2 in emergencies
when normal oxygen generators go down.
These candles are basically bigger versions
of the oxygen generators found on flights.
On May 11th, 1996,
ValuJet 592 took off from Miami International Airport.
Six minutes after takeoff, the crew heard a loud bang
and the Pilot, Captain Candi Kubeck, reported that they were
experiencing electrical problems.
Flight Attendants saw smoke in the cabin
and just three minutes later, the flight crashed
into the Everglades, killing all five crew
and all 105 passengers aboard.
Captain Kubeck had the unfortunate distinction of becoming
the first female pilot to die in a commercial plane crash.
So, what happened?
Underneath the front of the plane there were 144 expired
and soon to be expired, chemical oxygen generators
in the cargo compartment on their way to a ValuJet
facility in Atlanta.
A maintenance company had recently removed them
from two other planes.
Normally, you're supposed to put a safety cap
on these things to keep them from activating.
But this contractor was in a hurry and instead just wrapped
the discharge lanyard around the canister
and taped it in place.
This same contracted company would later be found guilty
for mishandling these hazardous materials
and one of their mechanics is still on the run from the FBI.
The oxygen generators wound up in ValuJet 592's
cargo compartment, loosely packed and unsecured.
An oxygen generator likely activated sometime
between loading and takeoff.
Maybe caused by a jolt on the runway,
which started a fire in the cargo hold
below the passenger's feet.
You might think that airplanes would have some sort
of fire suppression system in case a fire starts
in the cargo compartment.
And had this been a typical fire, they did.
The compartment was designed to have very little ventilation
with the idea that if a fire started,
it would quickly use up the available oxygen
and self extinguish.
Now, the idea of using a sealed compartment
to squelch a fire, isn't a bad one.
If I place a jar over a candle,
cutting off its oxygen supply,
it'll burn through the oxygen around it in the jar
and then go out.
Unfortunately, in the ValuJet accident,
what was on fire were literal oxygen generators.
So they were just pumping oxygen into the small space.
So what if we add an oxygen source to our candle setup?
If I let a jar sit over a mint plant for awhile,
the plant will give up oxygen.
When I place the oxygen rich jar over a candle,
the candle inside burns longer, than a candle
in a jar filled with just normal air.
The same thing happened in the ValuJet cargo compartment.
The release of oxygen from the generators,
kept the fire burning longer and hotter
than it would have otherwise.
And stored right beside the oxygen generators,
were three large airplane tires.
Investigators suspect that the extreme heat of the fire
caused the explosion of one of the tires.
Hence the loud bang that the cabin crew heard.
In fact, the fire got so hot that it melted
some of the aluminum structures of the airplane.
Meaning it likely reached over 1000 degrees Fahrenheit.
It quickly destroyed electrical connections
causing the pilots to lose control
and crash into the swampy Everglades below.
After the disaster,
new safety regulations were put in place.
More safety staff, better fire detection
and suppression systems.
So no more relying on it burning through
a limited supply of oxygen
And a ban on chemical oxygen generators as cargo
on passenger planes.