How Do Planes Have Oxygen? (Truths)

Have you ever looked out of a plane window at cruising altitude, somewhere around 35,000 feet and wondered: “How are we breathing up here?”

After all, if you were to stand on a mountaintop at just 15,000 feet, you’d probably need an oxygen mask.

So how do passengers and crew on airplanes survive, even thrive, at heights where the air is too thin to breathe?

In this post, we will break down exactly how airplanes provide oxygen to everyone on board.

Why Oxygen Is a Problem at High Altitudes

At sea level, the air is dense and full of oxygen about 21% of it, to be exact. That’s perfect for humans. But the higher you go, the thinner the air gets.

The oxygen level stays about the same, but the air pressure drops significantly. That means your lungs can’t absorb oxygen as effectively.

At 35,000 feet, the air pressure is so low that you’d pass out within seconds without help.

In fact, the oxygen available at that altitude is about a quarter of what you get at sea level. That’s why high-altitude breathing systems are essential in aviation.

How Cabin Pressurization Works

Pressurizing the Cabin

Commercial airplanes are designed to mimic the conditions at lower altitudes, usually the equivalent of being at 6,000 to 8,000 feet above sea level. This is done through a system called cabin pressurization.

So, how does it work?

Airplanes use air from the jet engines to pressurize the cabin. This air is called bleed air (it’s hot, compressed, and very clean because it’s taken from a part of the engine that doesn’t involve fuel combustion).

Step-by-Step: How Cabin Air Is Created

1. Air is bled from the engine compressor: It’s extremely hot and under high pressure.
2. It’s cooled down: The air goes through air conditioning units to reduce the temperature.
3. It’s mixed: A portion of this air is mixed with recirculated cabin air.
4. The air enters the cabin: It flows into the cabin at a controlled rate.
5. Pressure is maintained: Outflow valves let air escape gradually, keeping the cabin at the right pressure.

So while it may feel like you’re breathing “normal” air, it’s actually a carefully engineered balance of airflow and pressure that keeps everyone safe and comfortable.

Where the Oxygen Comes From

You might be surprised to learn that airplanes don’t carry massive tanks of oxygen for normal flights. Instead, the oxygen you breathe during a flight is regular air, just like on the ground, but pressurized and filtered.

However, there are oxygen systems on board for emergencies. Let’s explore both types:

1. Normal Cabin Air

• Sourced from the engines via bleed air.
• Compressed, cooled, filtered.
• Feels fresh and oxygen-rich.
• Kept at a comfortable pressure and humidity.

2. Emergency Oxygen Systems

When something goes wrong, like a sudden loss of cabin pressure, airplanes are equipped with emergency oxygen systems. This is when those yellow masks drop from above your seat.

But where does that oxygen come from?

Two Main Sources:

• Chemical Oxygen Generators: These are the most common on commercial planes. Each passenger seat is connected to a small generator. When you pull the mask, it ignites a chemical reaction that produces oxygen.
• Compressed Oxygen Tanks: These are typically reserved for the flight crew and medical emergencies. They provide pure oxygen through masks.

What Happens in an Emergency?

Cabin Pressure Loss

If the cabin suddenly loses pressure, due to a malfunction or structural issue, there’s no time to waste. You might feel light-headed, disoriented, or even faint within seconds. That’s where emergency oxygen masks come in.

What to Do When Masks Drop

1. Pull the mask toward you: This starts the flow of oxygen.
2. Place it over your nose and mouth: Secure it with the elastic band.
3. Breathe normally: Even though the bag may not inflate, oxygen is flowing.
4. Assist others after helping yourself: Always help yourself first, you’ll be no use if you’re unconscious.

The Role of Pilots and Crew

Pilots

• Have their own dedicated oxygen systems.
• Trained to detect and respond quickly to pressure loss.
• Perform emergency descents when necessary.

Flight Attendants

• Trained in using supplemental oxygen.
• Help passengers stay calm and secure masks.
• Use portable oxygen tanks for in-flight medical needs.

Oxygen in Private and Military Planes

Not all planes are pressurized like commercial jets.

Private Planes

• Small planes (like Cessnas) flying below 10,000 feet often don’t need cabin pressurization.
• Pilots may carry portable oxygen tanks for higher altitudes.

Military Aircraft

• Use sophisticated oxygen delivery systems.
• Pilots wear oxygen masks at all times due to extreme altitudes and speed.
• Planes may be unpressurized or semi-pressurized depending on the mission.

Frequently Asked Questions

1. Is the air in a plane recycled?

Yes, but don’t worry; it’s safe. About 50% of the air is fresh from the engines, and the other 50% is filtered and recirculated through HEPA filters, which remove bacteria, viruses, and dust.

2. Can you run out of oxygen on a plane?

Under normal conditions, no. The air supply is continuous. Emergency oxygen is limited, usually about 12 to 20 minutes, enough time for the pilot to descend to a safe altitude.

3. Why don’t planes just carry oxygen tanks for everyone?

Oxygen tanks are heavy and bulky. Chemical generators are lighter, compact, and reliable, making them ideal for short-term emergency use.

4. Is airplane oxygen pure?

Emergency oxygen is often close to pure or a high concentration. Normal cabin air, however, is just regular air with standard oxygen levels; only pressurized.