Cabin Decompression During Flight

cabin crew

Many air passengers did not know about what occurred during Cabin Decompression. I am not making you feel that they are not knowledgeable enough. I want to emphasize that they must have a safety awareness of the situation and understand they must be secured and doing oxygen masks and breaths in a few seconds. Otherwise, they would not control their brains and bodies (No oxygen, no life!).

This article will help both passengers and flight attendants to review their knowledge regarding this subject. Safety culture has a significant influence on what passengers do about aircraft depressurization issues.


 {getToc} $title={Table of Contents}


What happens when a plane loses cabin pressure?

Any failure of cabin pressurization above 10,000 feet required an emergency descent to 8,000 feet or the closest to that while maintaining the minimum safe altitude (MSA). Oxygen masks for each seat will drop down. The oxygen system has sufficient oxygen for all on board and gives the pilot adequate time to descent to below 8,000 feet where no emergency oxygen is required.

If passengers do not adhere to the safety policy - being secured and doing their oxygen masks and breathing as fast as possible- they may suffer from Hypoxia which may lead them to lose consciousness and subsequent loss of their lives.

Why does a plane lose cabin pressure?

Cabin decompression can occur due to a pressurization system malfunction, small air leak, or damage to the plane that causes a breach in the plane structure, enabling cabin air to escape outside the plane, for example, loss of a window, or a breach in the plane fuselage due to an explosion.

In addition, the atmospheric pressure will change in the cabin to form a low concentration of oxygen because the atmospheric pressure in the cabin will be going to equal the atmospheric pressure outside the plane.

The severity of the cabin decompression effects will depend on the type of cabin decompression and fast emergency response by the flight and cabin crew.


Types of Plane Cabin Decompression

There are two types of plane cabin decompression


1- Explosive Decompression

It is also widely known as rapid decompression in aircraft (plane), uncontrolled cabin decompression, it is occurred as a result of a sudden loss in cabin pressure, and can be recognized by the following physical signs:

The sign

The cause

1-      A loud bang, thump, or clap

As the result of the sudden contact between the internal and external masses of air.

2-       Cloud of fog or mist in the cabin

Due to the drop in temperature, and the change in humidity.

3-      A decrease in temperature

As the cabin temperature equalizes with the outside air temperature

4-      The release of the cabin oxygen masks

When the cabin altitude reaches 14 000 feet.

5-      Rush of air

As the air exits the cabin.


If a breach in the plane structure is the cause of the decompression. The following signs can be recognized:

• Unsecured items in the immediate area are ejected from the plane

• Debris may fly around the cabin

• Loose items may become projectiles

• Dust particles may limit visibility.


2- Slow Cabin Decompression

Slow cabin decompression can happen when there is a gradual decrease in cabin pressure due to a faulty door seal, cracked window, or a malfunction in the pressurization system.

Slow decompression may not always be noticed for this reason flight attendants and passengers may not notice the changes in the cabin pressure, until the oxygen masks drop down from the Passenger Service Units (PSUs).


Therefore, flight attendants and passengers must be aware of signs that could indicate a slow decompression. Example an unusual noise, such as:


-  whistling

-   hissing sound around the door areas,


This unusual noise is an indication of a slow decompression, therefore, if Flight Attendants notice these signs they must notify the flight crew immediately.

Further signs, due to gas expansion, one of the first physiological indications of a slow decompression may be :

Ear discomfort or ‘popping’,

-   Joint pain, or

-   Stomach pain



The lower partial pressure of oxygen at altitude reduces the alveolar oxygen tension in the lungs and subsequently in the brain, leading to sluggish thinking, dimmed vision, loss of consciousness, and ultimately death. Some passengers, particularly those with heart or lung disease may begin to feel the ill effects as low as 5000 feet, although most passengers can tolerate altitudes of 8000 feet without ill effects. At altitude, there is about 25% less oxygen than there is at sea level.


Time of Useful Consciousness

The time of useful consciousness refers to the time available to individuals to perform their tasks after they have been deprived of oxygen. But are still aware of their environment and capable of controlling their actions.





Moderate Activity


Sitting Quietly


22 000 feet

5 minutes

10 minutes

25 000 feet

2 minutes

3 minutes

28 000 feet

1 minute

1.5 minutes

30 000 feet

45 seconds

1.25 minutes

35 000 feet

30 seconds

45 seconds

40 000 feet

18 seconds

30 seconds


In the case of cabin decompression, the first actions by Flight Attendants and passengers should be:

- Donning the nearest oxygen mask;

- Sitting down and strapping in. secure self with seatbelt or harness

- If a flight attendant is unable to sit down, he should grasp the nearest fixed object or ask passengers to assist by holding on to avoid being ejected from the aircraft.


Maged Saeed AL-Hadabi

I’m Instructor / Maged Saeed Al-Hadabi. ​ Air Cargo / IATA Dangerous Goods Regulations / Safety Management System Senior Instructor, Auditor [ Yemen Airways] . Approved IATA DGR/ SMS Instructor by Yemen Civil Aviation Authority.

Previous Post Next Post

Contact Form