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Why Do Planes Have Oxygen Masks?

If you’ve ever paid attention during an in-flight safety demonstration (and hopefully, if you’ve flown in a plane, you have), you noticed that the flight attendants demonstrate how to put on oxygen masks. However, you hopefully never actually saw those masks. If passengers almost never have to use them, why do planes have oxygen masks in the first place?

Planes only need oxygen masks in case of an emergency, such as a drop in cabin pressure. Then, passengers breathe through the oxygen masks until the pilot can lower the plane to a safe altitude. Although most flights don’t need oxygen masks, every plane has them in case of an accident on board.

Here is what you need to know about this piece of equipment on board.

What Is the Point of Oxygen Masks?

You can fly your whole life without needing to use an oxygen mask, even though every plane you board is required to have some. Oxygen masks only drop when the air pressure in the cabin decreases. 

You may be wondering what air pressure has to do with oxygen and breathing. The higher the altitude, the lower the oxygen content in the air, which is why people report altitude sickness even when climbing to high areas firmly located on firm soil. The air in the lower levels of the atmosphere in which planes fly is even thinner in oxygen content.

To solve this problem, modern airplanes have cabin pressurization systems. This maintains the air pressure on board to what it would be like in a moderately high-altitude city on the ground, even if the atmosphere outside is much thinner. However, if the cabin depressurizes, then the system is not able to circulate enough oxygen for everyone.

In the event of such an emergency, which is very rare, oxygen masks will drop down from the ceiling panels. All passengers and crew have to put on their oxygen masks and breathe normally. The masks will keep everyone alive until the plane can safely decrease in altitude and land.

How Do Oxygen Masks Work?

When oxygen masks drop down, everyone who paid attention to the in-flight safety demonstrations should know what to do (of course, the reality is often different as panic affects your reaction time). Passengers and crew must pull the yellow mask part and place it over their noses and mouth. You don’t have to breathe any different when putting on an oxygen mask—just breathe as you normally would.

Despite their moniker, oxygen masks don’t actually contain oxygen. Instead, the compounds inside the masks are made up of several chemicals such as barium peroxide that combine with each other to mimic oxygen. There is a mechanism in the panels that sets the chemicals on fire, which triggers the reaction that releases oxygen.

There are a few reasons why airlines opt for this compound instead of pure oxygen. People still haven’t figured out how to transport oxygen in an efficient manner, and equipping airplanes with oxygen tanks for every person on board would be too bulky. Plus, oxygen is a volatile compound that easily catches fire—not an ideal combination on board a plane.

Pilots have to be the first people to put on their oxygen masks. Then, they will safely lower the plane to an altitude of 10,000 feet or lower. That is because the oxygen masks only have enough air to sustain people for 10-20 minutes (which is usually enough to reach a safe altitude). Below 10,000 feet, the atmosphere is stable enough for people to breathe normally as if on the ground.

Are Oxygen Masks Bad For You?

Some people are not sure about the efficacy of oxygen masks. A few people (usually those who watch too much Fight Club) believe that the oxygen airlines pump through the masks is to pacify passengers into accepting their deaths. However, oxygen in tanks does not have this euphoric, calming effect, which anyone who’s gone scuba diving can attest to.

Others raise questions about the potential health effects of the chemicals used to make up the air in the masks. Scientists admit that the long-term health effects of many of the chemicals in these compounds are not actually known yet. However, people will not inhale the chemicals in large enough quantities to cause lasting damage.

Whatever potential negative effects there are from oxygen masks, the effect of hypoxia is much worse. Hypoxia is a health condition that arises when the blood and tissues don’t have enough oxygen. A normal person can become hypoxic in just a few seconds of low cabin pressure. 

Short-term hypoxia causes impaired functioning and decision-making, among other symptoms. Long-term effects are far more severe, including seizures and even brain death. It’s certainly not worth risking your life—if you see an oxygen mask drop down, put it on first, and ask questions later.

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