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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.
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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
Hypoxia
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.
TIME
OF USEFUL CONSCIOUSNESS
|
||
|
Altitude |
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 |
Summary
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.