Hello, and Wellcome In case of decompression, an oxygen mask will be released automatically from the panel above your seat. Pull one mask towards you, place it over mouth and nose, and breathe normally, then assists others Um, Joe? Would you please start with your explanation? Sure. about a device you all have seen and heard before The passenger oxygen mask. We'll look at the mask in more detail. Why do you have to pull down on the mask? And what's that got to do with a cigarette lighter? So let's take one deep breath. And let's get started. Now as you know, the higher an airplane flies, the more the outside air pressure decreases making it harder to breathe. At 18,000 feet, there's only half of the oxygen left in the air. Now anyone who's climbed Kilimanjaro knows the feeling as more or less you have to breathe twice as fast to absorb the same amount of oxygen as if you are at sea level. If you go even higher and try to climb Mount Everest at 29,000 feet, there's only a quarter of oxygen left in the air. So that's why you often see pictures like this What the climbers carry on their shoulders is so-called supplementary oxygen, comparable to a scuba diver.
But how does that relate to us, passengers? Besides that a jet airliner is an engineering masterpiece, it also acts as a flying pressure chamber. Check the next time you get on board, you can see these big rubber seals around the cabin door, preventing the air from exiting or entering the cabin. So the air conditioning system creates the necessary air pressure within the pressure chamber/the cabin that you can comfortably breathe as if you were on the ground. Well, to be exact, once you climb beyond 10,000 feet, a pressurization system tries to keep the cabin at sea-level pressure. But, due to the structural limit of the cabin hole, which can only withstand a pressure difference between the outside and inside of up to 9 psi, the so-called cabin altitude will climb up to 8,000 feet. This means whilst the plane is in cruise at 38,000 feet, you as a passenger are in a cabin environment as if you'd be standing on a mountain at 8,000 feet. Now ever wondered why you get so sleepy on planes? That is one of the reasons. Now picture the scenario. Let's say we would have structural damage to the plane's cabin, a window popped out, for example, the cabin would experience a rapid decompression similar to the Southwest incident just recently. Now meaning the plane can't maintain the cabin altitude of 8,000 feet and rapidly equalizes to the outside pressure, having the effect that you've just climbed up to Mount Everest in a couple of seconds. In order to survive that, you need supplementary oxygen Considering this scenario, most jet airliners automatically deploy the passenger
oxygen mask from the panel above your seat as the system is triggered, detecting an excessive climb beyond 14,000 feet in cabin altitude. The imminent consequence is to descend the aircraft to a suitable altitude, so the passenger can breathe normally. Now the pilots will initiate a so-called Emergency Descent Procedure, very often done by memory as it requires immediate action, and one of these items is Passenger emergency oxygen masks on or deployed, in case the system was faulty and hasn't deployed them already. We now have all the oxygen masks dangling down from the panel above your seat. Now, what are you gonna do? Now let's first look at the mask in more detail. We have the lanyard or the hose leading to the mask. Now the mask itself is yellow made from soft plastic, including the rubber band to fit the snug mouth and nose and breathe normally, two valves on the mask, which open up as you exhale and close as you inhale the oxygen, and the transparent plastic reservoir bag. The bag allows for a bit of oxygen savings if the mask is situated well by mouth and nose. The oxygen will collect in the bag as you are exhaling, instead of seeping out at the sides of the mask, but I'll come back to that in a minute. But the main question is Where does the oxygen come from and why do I have to pull one mask towards you as flight attendant JOE seraphine showed early on?
If you want to start the flow on a scuba diver's oxygen bottle, you turn and don't pull. Well, it's hard to believe, but the oxygen flowing out of the mask is a result of a chemical reaction. In the housing of the panel above your seat sits this little cylindrical container, better known as Emergency Oxygen Generator. This container is filled with a mixture of sodium chlorate and iron powder. If you ignite the mixture, an unstoppable thermal chemical reaction unfolds and the evaporating gas of this reaction is... breathable oxygen. And the reason why you have to pull on your mask is It releases the pin from the striker assembly, the striker hits the percussion-cap, sparking an explosive charge, lighting the mixture, and starting the chemical reaction. Similar to a cigarette lighter you pull down or press, the button then creates a spark and lights to a mixture of air and gas. Now a few facts about the chemical oxygen generator No, one generator supplies oxygen for the seat row you're setting in, so if you're sitting in a row of three, You are sharing it with your two neighbors. No, the flow is fairly constant and continuous, equally spread out to all users. Well to be precise, the amount of oxygen required at higher altitudes will be greater than needed at lower altitudes. Therefore, the chemical core of the generator has a larger diameter first, generating more oxygen after initiation as you are still high up in the sky and need more oxygen. The generator will supply a flow of low-pressure oxygen for a minimum of 15 minutes, equivalent to the time the pilots will need to descend to a minimum of 14,000 feet, where the air is dense enough for you to breathe without the mask. This is very unlikely to happen, as all oxygen panels simultaneously get an electrical signal to open up.
But in case yours fails, give it a bit of a bang with your hand, as it is only held up with minor force and should then fall out. If it's still not coming down, the flight attendant has to come around with a pin, which fits into that little hole to manually open the panel. I admit you're having a really bad day as it is if that happens. Well if you act quickly and there's an empty seat ahead of you, you could just swap seats real quick. Stay put, there is a minimum of two oxygen masks in each lavatory. This more or less shows how well you deal with the emergency situation. Some passengers stay calm and so the bag will fill slowly as they need less oxygen, but also can indicate you've just passed out and barely breathing whilst the bag fills to the max. But please don't mistake this bag for a paper bag you place it over your mouth and nose in case you're hyperventilating, that's a whole another story. Now during the chemical reaction, the generator becomes extremely hot to up to 250 degrees Celsius and the plastic casing around it dissipates some burning smell, but don't worry. Any indication of an excessive cabin altitude will trigger the master warning in the cockpit. Pilots immediately placed a quick donning mask over their head within seconds, which can supply, depending on the setting, 100% oxygen for several hours. And those masks are covered in another blog. Now the cabin crew primarily uses the same oxygen supply as the passengers do, but have the option to use pressurized oxygen bottles, which they can carry around more or less like a handbag, giving them more flexibility to walk around and prepare the cabin and passengers according to the emergency situation. There should always be 10% more masks than passengers on board. It's a legal requirement. The primary reason planes don't have large oxygen bottles is the weight.
The chemical generators only weigh a third of the bottles for the same amount of oxygen and are a lot cheaper to install and maintain. But hold that thought, because there are a few rare planes out there, which have emergency oxygen for passengers in large pressurized bottles. A few Airbus A340 are installed with such an emergency oxygen system for one reason only If the airline chooses to fly a specific route over the Himalayas, the so-called drift down or escape procedure in case of a failure takes more than 30 minutes to be at an altitude lower than 14,000 feet, so these airlines had to fit their planes with large pressurized oxygen tanks to provide the necessary safety on that specific route.
Why am I not surprised that that route goes behind Mount Everest? So please do yourself a favor and the next time you board a plane, listen and watch carefully for the safety demonstration of the flight attendants. I don't care if you've seen it a hundred times and you think you know it all. In a panic situation, you will act differently. Trust me. So show some respect and don't play around with your phone, because if you fainting out cause you're wearing the mask like this guy, I am not gonna be the guy, who puts his mask on first and would be helping others. I mean, look at this guy. He's got the time to take a selfie. His mate next to him, he's checking his emails as you're doing an emergency. Ridiculous. That's it for today. Thank you very much for your time.
