The air we breathe on airplanes and pressurization

In this new installment we will learn about the air we breathe on airplanes and cóhow does it work pressurization systemón of the aircraft.

Post written by: Capturesán Rodolfo Estrella
FAA Commercial Pilot
Twitter: @rodo_estrella

At the end of last September, presentó a news item on CNN whereíto the title  from “A terrifying moment in the air: I saw oneóI came down from the Deltaó 9.000 meters suddenly”.

a tísensational title so it must be demystified with respect to cóhow does the avi workón, your environmental system, the pressurizationón and because maneuvers that can cause fear are sometimes necessary.

The air we breathe

To understand how pressurization systems workón and atmosphereón of an aircraft, We first have to know the air we normally breathe in the environment and the effect it has on our body when a condition exists.ón of lack of oxígeno.

The normal ambient air that we all breathe at any time isá subject to pressureón atmosphereérica, take thisón exerted on all bodies is greater at sea level and less in places like Quito or La Paz, high altitude cities.

We have theído that the oxígeno is smaller in the heights but it is incorrect, throughout the atmosphere the percentage of oxígeno is constant around 21%, the difference isá in which the concentrationón of this is lower per parcel of air thanks to a lower pressureón atmosphereérica.

Imagine a parcel of air 1 square meter, at sea level it will haveá all the weight of the atmosphere on it, Although we believe that this weight is not felt, this exists, The weight of the atmosphere is caused by the force that planetary gravity exerts on all things including the air and the atmosphere., This weight at sea level makes the partsíox cellsígeno isén más concentrated and therefore there are many partsíox cellsígeno concentrated in said plot, are you partíox cellsígeno isán más stuck to each other so to speakí, but if we take this parcel of air to a much higher altitude, the weight of the atmosphere on it is less so there is less atmosphere on it exerting pressureón, that makes the partsíox cellsígeno isén exposed to lower pressureón and that causes a lower concentrationón the oxígeno, the partsícells expand, causing their concentration in that same parcel of airón the oxígeno is less.

Then, I saw oneón that flies at very high altitudes produceíbecause in the passenger cabin the concentrationón the oxígen in the air is very low, producing an effect known as Hypoxia in its occupants..

Hypoxia in general terms is a conditionón of lack of oxígene in the body, At higher altitudes, the body's response to staying conscious is drastically reduced.ástically due to lack of oxígeno becoming very few seconds when the altitudes exceed the 35.000 O 40.000 pies. But its first effects can be observed at much lower altitudes from 10.000 O 12.000 pies.

Eventually being exposed to this conditionón of lack of oxígene leads to death since we all know that the human body needs oxygenígene to live.

Then, ¿cóWhy can we fly so high and be able to breathe in the plane?ón? Very easy, It's because of the pressurization system.ón.

Pressurizationón

The pressurization systemón is a system that provides the sectionópressurized aircraftón, that is, the inhabitant(s)áasses to beán occupied by people or living beings a pressureón of air equivalent to a lower altitude, in this way the concentrationón the oxígeno is set at a level where the occupants can breathe normally.

¿Cóhow pressurization is achievedón?

Not all systems are equal and varyístill in its avi operationón in avión, but generally the system consists of obtaining pressurized airón coming from the turbine engines to “fill out” the cabin.

This air comes from the sectionóno call tooéin the compression stageón of a turbine engine, where air is taken from the environment and by means of compressors it is compressed to feed the following phases of turbine power, In the middle of these compression stagesón clean air there are the so-called “vábleeding valves” that extract some of that hot compressed air and redirect it throughés of filters and pressure regulating systemsón towards the cabin.

It's a different storyón is regulated to provide a pressureón “atmosphereérica” simulated to the cabin  is equivalent to a catchóAt a much lower altitude this air is known as pressurized air.

This effect of introducing air with pressureón major inside the airplane cabinón produces a force on the fuselage, a force that struggles to get out, therefore, The emergency doors are tap typeón and in flight by máIf you exert any force, you cannot open them because to open them inward you have to overcome the pressurization force.ón exercised on this.

It should be noted, than the grandfatherón between más nearby is grounded, in descent for example, I took itón internal pressure is approachingón external, opening the possibility of an emergency door, could be fíphysically open in flight.

Then, this air that leaves the engines enters hot, since an effect of applying pressureón on a mass of air is to increase its temperature for this reason causingíto a pressurized cabin but incófashionably hot, so the system mixes this hot air with cold outside air to regulate its temperature or an air conditioning system works together.

Clean Air

The air that enters the cabin for pressurizationóIt is not like a balloon that inflates and stays that way.í all the time. All the air that enters isá in constant circulationón y modulationótemperature, that is, always beá fresco. And the system is kept constantly pressurized with fresh air.

On the pressure bulkheadsón usually located in the back there are váregulating valves that maintain pressureón selected from the cabin and maintain an exhaust air flow, así as wellén exist vásafety valves that activateúeven in case of failure of the váregulating valves and allow depressurization if necessary or to maintain the aircraftón depressurized on land.

Usually the passenger feels that the air has a strange atmosphere, sometimes it can even smell, this is because the air comes from the motors, goes through filters, regulators, circulation channelsón, grids, etc. where it collects impurities from the system but as mentionedó previously, since this comes from a sectionón clean engine there is no danger of contaminated air.

emergencies

Returning to the case of the Delta flight, now that we know cóhow the pressurization system worksón and cóThis provides us with a cabin that gives us the comfort of being able to breathe calmly with a pressureóhigh air pressure, spaghettiéWe must not think that how is a system, this is prone to fail at any time.

Then, ¿thaté happens if the system fails or if there is a depressurizationón in cabin?

For these cases there are emergency procedures, where the priority of the crewón is to descend to an altitude at which all occupants can breathe normally, for this you must proceed with an emergency descent, Apparently it may seem like a dangerous procedure, but the maneuver is normal and very necessary..

The first thing we will have as passengers is the presentationón of máox scarasígeno, these provide oxygenígeno to breathe normally temporarily but these masks do not have a sufficient amount of oxygenígene for the entire durationón of the flight so it is a priority to get to the planeón at an altitude máIt goes down where the concentration isón the oxíGeno allow a breathón normal given that, as already mentionedó consciousness time at high altitudes without oxígeno is just a few seconds so we proceed to descend as much as possible.ás ráI ask possible by generating that a sensationón of “terror” in the passengers, However, it is a normal procedure and very necessary to avoid damage.ños on the health of the occupants.

Now that we know how pressurization worksón, the environmental system and what happens if these fail, we are sure that if at some pointúAt some point we have to face an emergency of this type, we will know how to act calmly, with the assurance that the crewón does everything possible for the immediate well-being and health of everyone and by staying calm you can even help other passengers stay calm.