Where does the air for breathing come from?

A participant in my fearless flight program said that one of the reasons for her anxiety about flying is the fear of a situation where the air to breathe on the plane will run out. She especially developed a fear of flying when the plane was delayed before takeoff because she feared that during this time, they were breathing the oxygen that passengers would need later in the flight. This is one of many examples that explains why knowledge is power. After a ten-minute explanation, she realized that this fear was not based on reality. So for all those who have a fear of flying like that participant, or those who are frightened by the safety video showing the use of oxygen masks on board a plane, let’s discuss the issue of air pressure in the plane, the oxygen we breathe, and also – what happens when there are disruptions.

Some theory about breathable air

The composition of air in the atmosphere is constant. Each unit of volume of air has about 20% oxygen, and the rest of the air, for the most part consists of nitrogen. We need to breathe oxygen, and every breath needs a given amount of oxygen. Lack of oxygen causes a phenomenon called hypoxia and depending on the severity of the lack of oxygen, we will quickly lose consciousness, and if we do not receive oxygen, we will die. Physical law states that although the percentage of oxygen remains constant in all layers of the atmosphere, the amount of oxygen per unit volume decreases as the air pressure decreases. As the altitude increases, the air pressure decreases. In high mountains, the air is known to be ‘thin’, and at particularly high altitudes, such as those where passenger planes fly, the air pressure is insufficient for a person to survive.

The compression system in aircraft

To accommodate the passengers, the fuselage is compressed by outside air, which has been compressed in the aircraft engines, thus maintaining a suitable pressure that allows free breathing in the aircraft. So that the plane is not compressed indefinitely, a special valve usually located in the rear part of the plane releases the air in a controlled manner and maintains the desired pressure. 

 If so it can be understood that the air in the plane is simply outside air. It can not finish, it is very clean of soot, pollution, dust, and bacteria and after a short stay on the plane it comes out. Like any critical passenger aircraft system, the compression system consists of several independent components so that a malfunction in one of them will not cause the air pressure in the aircraft to drop. But what happens if a failure in the structure of the aircraft causes the pressure to release? Such malfunctions are rare, and one of the most serious known to us occurred recently, on April 17, 2018. The disintegration of part of the aircraft of a Southwest Airline 737 caused part of the engine to fly towards the fuselage, tearing a hole in the side of the aircraft, through which a passenger was sucked out. Although the passengers pulled her in, she died, apparently from exposure to the extreme cold and lack of oxygen. The other passengers, who were wearing the oxygen masks, came out unscathed.

Is there a risk of contracting the disease in flight?

In early 2016, measles began to spread in Europe, with more than 6,000 cases reported in 30 countries, including Germany, Romania, Austria, France, Italy, Portugal, Spain, Sweden and more. Experts estimate that in practice there are more cases than those reported. In 2019 a number of cases of people being infected with measles were reported probably during a flight. The question is what is the risk in flight in terms of contracting the disease. Infection is done by contact with the disease bacteria. In-flight we breathe air that came from outside, and the chances that this air will contain some bacteria are very low. However, on a crowded plane, there 

may be passengers or crew members who are ill, and the risk of contracting them exists. It should still be remembered that the air in the plane changes at a fast pace and therefore this chance in my estimation is much lower than the chance of catching the disease in a restaurant, in a movie or at any gathering that takes place indoors.

February 2020 – Corona virus

At the time of writing, the world is in chaos, when a virus known as corona has already killed cavities in China and elsewhere. Everything said in this article is also true for the same virus. The air in the planes comes from outside and leaves the plane after a short stay. There is no standing air in the plane. However, it is important to remember that a person sitting next to you on a plane can infect you, much like a person on a bus, in a cafe, or on the street can do. For a newer article about flying during COVID 19 – follow this link.

What happens when the pressure in the plane drops?

A case in which an opening in the cabin opens is very rare. A drop in pressure can happen for other reasons, and the plane is built to provide a solution that will allow all passengers to reach the ground safely. Above each group of seats on the plane is installed an automatic system, which is activated in a pressure drop. Oxygen masks are then released in the greater number of seats in the same group of seats. These masks allow each passenger to get enough air to breathe until the plane reaches a lower altitude where it is possible to breathe air at a sufficient pressure. It happens at an altitude of 10,000 feet, about 3 miles.

Passengers with oxygen masks – it is mandatory to wear them on the mouth and nose and not as the passengers did in the photo (Photo: AP, Marty Martinez)

In case the air pressure in the plane did drop, and the masks came loose, the most important thing is to wear a mask, first your own and then help the environment. Every second counts, and if you faint from lack of oxygen you will not be able to help others. If this happens to you when you are not in your seat, in the aisle, for example, reach out and grab a mask from one of your sides. Remember that masks fall higher than each group of seats (usually one more) than the number of seats. The toilet also has an oxygen mask. The most important thing is to wear a mask, we already said… right? At the same time, the pilots will start performing an emergency descent, and you will feel the plane lowering. To this feeling of descent will be added vibrations resulting from the speed brakes, which are surfaces that rise above the wings’ surfaces and help to lose height quickly. Such a descent may take about ten minutes, at the end of which the passengers and flight attendants will be able to take off their masks.

Air onboard a plane – summary

  • The breathable air in the cabin comes from outside
  • It is compressed and heated to the required conditions
  • The air in the plane changes at a high rate
  • In case of pressure drop in the plane, it is most important to wear an oxygen mask