Breathe without oxygen: where does the air in the cabin

© Depositphotos / CandyBoxImagesСтюардесса briefingBreathe without oxygen: where does the air in the cabin© Depositphotos / CandyBoxImages

The average flight altitude passenger aircraft is 9-12 thousand meters. The air in this part of the atmosphere is much rarefied, and its temperature below -45 0C. However, in the interior of the liner conditions are always relatively comfortable. This is not only good insulation, but also a complex system that allows you to convert the outside into breathable. And yet, if you look, the conditions do not correspond to the usual terrestrial atmosphere.

In the early era of aviation, aircraft were doing is completely sealed, but due to strong pressure difference inside and outside the aircraft, the metal is stretched, which led to the destruction of the structure. So at the moment in the salon maintain a lower pressure than what corresponds to the level of the airport.

However, too little compression of the air in the cabin can give passengers a strong discomfort by reducing the force with which the oxygen pressure on the walls of blood vessels. The height of 2500 meters corresponds to the top pressure when the blood normally saturated with oxygen, and the person is not experiencing headaches, shortness of breath, nausea and extreme fatigue. Most often when flight is maintained at a pressure corresponding to the altitude of 1300-1800 meters, that is, 600-650 mm Hg.

When you inhale an adult consumes an average of 0.0005 cubic meter of air. The minute we make an average of 18 respiratory cycles, recycling during this time of 0.009 cubic meter of air. It seems that a little bit. But the interior of the liner has an average of 600 passengers, therefore, the minute all of them requires 5.4 cubic meters of air. The air gradually «contaminated», the oxygen content in it decreases and after a while breathing becomes simply impossible. Therefore, for comfort (and in General to sustain) passengers needed fresh air into the cabin.

All modern aircraft are equipped with a system that simultaneously provides the cabin with oxygen and supports the work of the engine, as the fuel in it is burned only in the oxidation with oxygen. When air from the atmosphere gets into the inner circuit of the engine, it is highly compressed and thereby heated. Next, from one stage of the compressor (a device for compression of the gaseous substance) the air is taken already for a salon. The fence is before mixing with the fuel, so it is absolutely harmless and clean, but just in case it is still forced through the filters.

CC BY-SA 2.0 / Jeff Dahi, Alina Polyanina / diagram of the engine of the planeBreathe without oxygen: where does the air in the cabinCC BY-SA 2.0 / Jeff Dahi, Alina Polyanina / diagram of the engine of the plane

The temperature of the heated engine air amounts to about 500 0C. Therefore, before entering the salon he goes to the radiator (the device for heat dissipation), where it is cooled and then enters the cooling turbine, rotating the turbine through its expansion. The energy of the air decreases, the temperature falls to 2 0C.

As a result, in the interior fall into two different airflow: hot, which has not gone through the cooling turbine, and cold passed through him. The pilot controls the cabin temperature by mixing hot and cold air in the correct proportions.

© Illustration RIA Novosti . Alina Polymineralic air temperature in the cabinBreathe without oxygen: where does the air in the cabin© Illustration RIA Novosti . Alina Polymineralic air temperature in the cabin

The main drawback of the system lies in the fact that the air entering the cabin, too dry. Sparse in the atmosphere, it contains less moisture, and if the interior is in addition. This is done in order that the pipes of the air conditioning system did not demersal ice, which can lead to blockage. That is why many passengers complain of dry eyes and throat during the flight.