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How do airplane cabin passenger oxygen masks work?

Do you seriously pay attention to the passenger oxygen mask demonstration when you fly? Well, should your oxygen mask come down inflight, you’d better know the importance of putting it on correctly.

Not donning your oxygen mask correctly could hurt you!

What are Passenger Oxygen Masks?

Passenger oxygen masks deployed.

Airplane cabin passenger oxygen masks are designed to supply you with oxygen until your pilots can get the plane down to below 10,000 feet sea level altitude.

If the airplane cabin pressure drops to where the masks come down you need to don your mask in order for your body to continue functioning normally.

Do pilots use the same type of oxygen masks as passengers?

B737 pilot oxygen mask
Pilot oxygen mask.

No, the pilots use a different type of oxygen mask. Their masks are hooked up to a separate oxygen bottle system for the flight deck only.

The pilot mask-system is also equipped with oxygen flow pressure regulators, a communication microphone, air-pressure straps ensuring a snug fit, and smoke goggles if needed in addition to the oxygen.

The pilot oxygen mask straps go around the head when quick-donning the mask with one hand from the mask compartment.

What type of oxygen masks do flight attendants use?

Flight attendant masks are identical to those of the passenger masks. In addition, flight attendants have access to the onboard portable oxygen bottles, designed for medical emergencies.

The air inside your airplane cabin

The thickness of the air molecules outside your plane at a typical cruising altitude of let’s say 37,000 feet is so thin that you would lose consciousness within a few seconds. However, the air inside your airplane cabin is never pressurized to a height of more than about 8,000 feet.

Breathing in the “thickness” of that 8,000 feet cabin air would be the same as breathing the air located on an 8,000-foot tall mountain.

Why is it important to wear your mask snuggly fastened around your mouth AND nose?

Place your mask tightly around your entire mouth and nose. Otherwise, oxygen will seep out of the side of the mask, decreasing the amount of oxygen intended for your body!

Southwest flight 1380 loss of pressurization

Passenger Marty Martinez was quite a Gentleman for coming forward with his picture of passengers wearing oxygen masks during this incident. It has since served as a great educational image for the importance of situational awareness should you ever have to don your oxygen mask on a flight.

The picture below represents a prime example of how a passenger oxygen mask should NOT be worn. Here we can see how passengers are wearing the mask incorrectly. The mask is not covering the NOSE.

passenger oxygen masks worn incorrectly

However, the end result of this incident went well, fortunately.

Hint: Paying careful attention to the flight attendant’s safety demo prior to the flight should have prevented this passenger-mistake from happening.

Video-report of the Southwest 1380 oxygen mask incident

Southwest Airlines flight oxygen mask deployment and emergency landing. CBS Local News/YouTube.

How is the passenger oxygen mask made?

The yellow-colored mask consists of a soft plastic material. You’ll find two valves inside the mask, one opens for exhaling and the other opens for inhaling.

Why do you have to pull down on the mask to initiate the flow of oxygen?

When you pull on the lanyard (string) attached to the mask you activate a firing pin in the oxygen canister mechanism. You can compare the firing pin with that of a lighter. Flick the lighter and you will have a spark.

The flow of oxygen is activated by a chemical reaction using a generator inside a cylinder, filled with a mixture of sodium chloride (NaCl) and iron powder.

Igniting the sodium chloride and iron powder mixture creates a thermal reaction that evaporates into a gas (Oxygen).

Oxygen flows to your mask through the clear plastic tubing between your overhead canister and mask.

Is there one oxygen generator for every mask?

No. One generator supplies your entire seat row.

Can you control the flow of passenger oxygen?

No, you cannot control the oxygen flow. It does, however, have an automatic regulator. The oxygen flow is proportionate to the altitude of the cabin. The higher up you are the higher the flow coming out.

Does the bag attached to your mask inflate?

Not necessarily. Each mask assembly has been designed to automatically provide oxygen flow to each mask, depending on how much oxygen you need individually. If you are the calm type who puts on your mask and breath normally the bag probably won’t inflate.

However, if you panic and start breathing excessively the bag would most likely inflate, because of your rapid “panic breathing”.

How long do passenger oxygen masks provide oxygen?

The system has been designed to provide a minimum of 15 minutes of oxygen. This is just long enough for the pilots to descend to an altitude below 10,000 feet, where supplemental oxygen is no longer required by most people.

How do the passenger oxygen masks come down?

The masks are held in place by doors above the passenger seats. the doors are automatically released by an electrical signal when the cabin altitude exceeds a certain height, typically 12,500 feet.

Should the door above you not open with the other oxygen doors opened, simply push a sharp object such as a hair pin into the small pin-hole in the door to get it released.

Oxygen mask door
The oxygen panel door pinhole release is to the right.

In addition, and as a backup, the pilots can manually release the doors from the cockpit pushing a guarded switch (see picture below).

Red arrow: Passenger oxygen mask door manual release switch, B757.

Is there an oxygen mask in the lavatory?

Yes, there is. There is a minimum of two masks inside each lavatory.

Why are there more oxygen masks than there are seats on the airplane?

This is a safety feature ensuring extra mask availability for malfunctioning masks, a lap child in the seat row, as well as the flight attendant’s need for mask usage if located next to you.

Regulations require an airplane to have a quantity of 10% more masks than what’s needed.

Hypoxia: What happens to our bodies if you don’t don the passenger oxygen mask?

Hypoxia is a deficiency of oxygen in the blood, tissues, and cells. With a lack of sufficient oxygen, we could get to the point where the deficiency causes impairment of body functions and the ability to think clearly.

How long does it take before you lose consciousness of you don’t put on your passenger oxygen mask?

It depends on what altitude your cabin gets to. For example, is your plane experiencing a rapid decompression or a gradual decompression?

The graphic below explains how long it takes for an average person to become unconscious from lack of oxygen if you don’t put your oxygen mask on. It tells us how long we can last under inadequate oxygen supply.

Let’s say your airplane has a total loss of cabin pressurization flying at 40,000 feet. You only have 15-20 seconds before you lose consciousness unless you don your oxygen mask! TUC means Time of Useful Consciousness. EPT means Effective Performance Time, another word for the same thing. Source: USAF Flight Surgeon.

How long can you survive without oxygen?

According to FAA Flight Surgeon literature, a complete absence of oxygen can cause death in approximately five to eight minutes!

Why you should put on your mask first

Always don your own oxygen mask first, to ensure you stay clear-headed. Otherwise, you cannot help others who may need help with putting on their masks.

Video demonstration from a military altitude chamber

Here’s a video showing you how you could become incapacitated if you don’t don your oxygen mask if they come down.

In this video, you can see how the airmen’s mental capabilities are gradually becoming unmanageable at a 25,000 feet altitude until their oxygen masks are donned. Video: YouTube.

How hot does a passenger oxygen mask cannister get?

It gets hot enough to burn your hand or fingers!

CAUTION! Do NOT reach up to the oxygen mask panel. The oxygen generating canister can reach a temperature of 500 degrees Fahrenheit (260 degrees Celcius)!

You will most likely sense the burning smell of the chemical reaction as well as the heat from the oxygen canisters.

This burning smell is completely normal, so don’t get alarmed.

When and how do airplane cabin oxygen masks drop?

The masks come down by two means: Automatically and by a manual release switch, activated by your pilots. The masks automatically drop if the cabin altitude exceeds about 12,500 feet.

Do passenger oxygen masks protect us from breathing in smoke in a cabin fire?

What you breathe in from the chemically made cannister oxygen is actually a mixture of air taken from the cabin, regardless of cabin altitude. Thus, your passenger oxygen mask will not prevent you from breathing in some cabin smoke.

Rapid decompression

Most cabin altitude problems involve a slow decrease in cabin pressure, with plenty of time for the pilots to correct or act on the situation before the masks come down.

A very fast (rapid) decompression, however, is an extremely rare event, but it has happened. A big enough hole or opening anywhere along the pressurized and sealed portion of the airplane (airplane body, door or window) could result in the cabin depressurizing immediately.

A rapid decompression is also likely to fog up the cabin, because of the sudden temperature change when outside air enters. The temperature inside the cabin may become very cold with outside air entering too. Depending on the length of the decompression event hypothermia may become a factor.

Varieties of the typical chemical passenger oxygen masks

Some airplanes used for flights over very high mountainous terrain have been equipped with individual passenger oxygen bottles, as opposed to chemical oxygen generators.

The reason for this is that these airplanes may be too far from a point where they can descend the plane to below 10,000 feet within about 15 minutes. Let’s say you’re over the Himalayas when the depressurization occurs. For example, it may take 45 minutes before your plane can get out of the tall mountain region before they can safely descend to below 10,000 feet.

How do pilots handle a depressurization event?

When the cabin altitude climbs above 10,000 feet an altitude warning horn sounds on the flight deck. A warning light also comes on. At that time your pilots will immediately don their oxygen masks and evaluate the situation, applying a checklist:

Cabin altitude warning or rapid depressurization-emergency descent immediate action items checklist
Cabin Altitude Warning or Rapid Depressurization/Emergency Descent Immediate Action items. Photo: B737 manual.

After that, the pilots will take further action, as necessary, following a series of other items to accomplish on that checklist.

Comments or questions? You can contact Captain Les here.

Featured Image: David Hancock/Alamy Stock Photo. Other photos, unless indicated: CaptainJetson.com

Do you want to learn about other potential health hazards when you fly? Then don’t miss 13 Bad Health Risks Of Flying.

Author Disclaimer. Captain Les:

  • Is not a medical professional, nor is he qualified to give medical advice to anyone. Consult a qualified medical professional for any medical advice you may need.
  • Is a licensed and qualified airline captain and flight instructor with a vast amount of education, knowledge, expertise, within all matters relating to his professional qualifications to flying jets as a pilot. This knowledge includes the USAF-, USN-, and the FAA-required pilot knowledge of aviation medicine.
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Why do planes have passenger oxygen masks?

Passenger emergency oxygen masks are installed in all airplanes to provide supplemental oxygen to each person in the airplane cabin in the event of a cabin decompression. Normally the air pressure inside plane’s cabin provide sufficient oxygen for breathing. If the cabin pressure drops as a result of pressurization failure or an opening (hole) in the airplane, the oxygen masks provides the needed oxygen for at least 15 minutes to prevent hypoxia.

How many minutes of oxygen do passenger oxygen masks provide?

Passenger oxygen masks provide oxygen an average of 15 minutes, with a varying range of passenger oxygen supply for 12 to 20 minutes, according to the FAA. This duration provides enough time for the pilots to descend to a sea level altitude of below 10,000, where supplemental oxygen is no longer required for most people.

How long can you survive without oxygen?

You can survive without oxygen for approximately five to eight minutes, according to the FAA Flight Surgeon. Once the oxygen level in your blood decreases to about 60% death can rapidly occur.

How do you wear a passenger oxygen mask properly on a plane?

Correct placement of a passenger oxygen mask requires placing the mask over your mouth AND nose. Otherwise, the oxygen meant for the passenger can seep out from the sides between the mask and the passenger’s face, which could quickly cause a lack of sufficient oxygen supply, leading to dangerous hypoxia.

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