The only reason you can breathe on an airplane is because the crew keeps the cabin pressurized. A Ryanair airline flight, departing from Dublin, was bound for the city of Zara. The plane was forced to face an emergency landing in the city of Frankfurt due to the depressurization of the aircraft cabin. Because of this, 33 of the 189 passengers on the plane presented discomfort and bleeding from their ears.

Also, cases in which people try to take a flight through the plane’s undercarriage are not at all rare: the BBC cites that since 1947 there have been 105 cases. Of those 105, 80 have ended in the death of the subject. Sometimes, however, people manage to survive thanks to the heat spread by electrical systems and accumulated by tires. The rapid ascent can also cause greater fatigue of the nervous system and, therefore, a demand by the brain for less oxygen.

What exactly does pressurized cabin mean?

During a normal flight, an airplane flies about 10,000 meters above the ground, an altitude higher than that of the Everest itself.At this height it is almost impossible to breathe, the air is too thin and, therefore, the oxygen particles present are too far apart.

Small planes and helicopters don’t fly very high and, therefore, don’t need pressurization. When they do need to fly long distances, big planes save a lot of time in travel by traveling much higher than the 3,000-meter threshold. This way they consume less fuel, since air resistance is considerably lower. In addition, turbulence and adverse weather conditions are avoided at those heights.Beyond the 3000m altitude, cabin pressurization becomes mandatory.

How do you pressurize a cabin?

The fuselage of an airplane is a “tube” capable of holding a large pressure difference between the inside and outside of the vehicle. Pressurization systems are active throughout the flight and, control the pressure through outflow valves that are usually located in the tail area.

The pressure inside the cabin is not what we feel at sea level. Such a high pressure difference would cause the fuselage to explode. The pressure in the pressurized cabin during flight at 10,000 meters is what we would find at about 2,000 meters.

The air coming from the engines is probably cleaner than the air in our homes. At first it is cleaned through a filtering system, then it is cooled and, finally, all the humidity is removed before arriving in the cabin. A computer manages autonomously the air pressure inside the fuselage so, the whole process is automatic.

What would happen if the cabin was not pressurized and, what is the hypoxia?

Breathing would be difficult, you would try to bring air to your lungs, but you would not have enough oxygen.From the lungs, blood transfers oxygen to all the internal organs, such as muscles, cells and, most importantly, your brain. It extremely needs oxygen to keep you conscious. If your body doesn’t get enough oxygen, it can lead to a condition called “hypoxia”which, as a first effect, causes you to pass out.

Hypoxia causes the human body to experience nausea, dizziness, shortness of breath, sweating and disorientation. Another common symptom, also easy to notice in fellow passengers, is continuous yawning. If the pressurized cabin should suddenly lose pressure, oxygen masks will drop from the ceiling. At this time, all passengers must put on their masks and breathe as normally as possible.

How does the pressurization system work?

Before departing, the aircraft keeps the exhaust valves open. Once all passengers have boarded, the pilots set the flight profile between the two airports in the computer and then set the air pressure regulator. As the plane is climbing during takeoff, those exhaust valves automatically close. It is advisable to use chewing gum at this juncture, which will help limit the discomfort to your eardrums.

It takes about 20 minutes for the aircraft to reach 10,000 metres so, the air pressure rises steadily with it and, on landing, the process will be the reverse: when it is time to start descending, the pilots set the airport altitude and, the cabin pressure will drop at a controlled rate.

How were the first flights with pressurization dealt with? Pilots and passengers at the time suffered from hypoxia. Engineers of the time had difficulty finding a solution. Bizarre methods were tried: they wore masks with a rubber tube for breathing with an oxygen cylinder. Needless to say, this was not an effective method. As a result, pressurization systems were the products in the 1930s. The windows were reinforced, while the cabin was sealed. The system needed fine-tuning, but slowly, we broke down this obstacle.