Decompression

Decompression

Aircraft cabins are pressurized for the comfort and safety of passengers and crewmembers. A loss of cabin pressure, decompression, is a rare occurrence that can take place on three levels. Keep in mind, an aircraft decompression can occur anywhere in the plane, even in the flight deck.

Insidious decompression:

• No visible indications.
• May hear whistling or noise near a window or door.
• Crew and passengers may become listless and sleepy, hypoxic.
• Oxygen masks may drop.
• May be advised of the situation by the flight crew before any visible signs are apparent.

Note: When flying at or above 14,000 feet and an insidious decompression occurs, oxygen masks will drop, which should be an immediate cause for all flight attendants to react and take action.

Rapid decompression:

• Some structural damage to aircraft may occur.
• Loud noise, and a rush of cabin air toward the damaged area.
• Fogging/misting in the cabin. The air temperature will drop substantially.
• Loose articles will fly within the cabin.
• Oxygen masks will drop.
• Aircraft will initiate a rapid descent attitude (severe nose-down attitude).
• Ears will pop and air will be forced from your body.
• Crewmembers and passengers may exhibit signs of hypoxia.

Explosive decompression:

• Sudden structural damage to aircraft.
• Large explosion, very loud noise.
• Air is sucked out of cabin causing everything not secured to fly through the cabin toward the opening. The presence of fog may occur.
• Oxygen masks will drop.
• Aircraft will initiate a rapid descent (severe nose down attitude).
• Ears will pop and air will be forced from body.
• Crew and passengers may exhibit signs of hypoxia.

Although the physical signs and cabin characteristics are different for each level, the procedure is the same – use oxygen immediately.  Without oxygen, people will lose consciousness rapidly.

Time of useful consciousness

This is the amount of time in which a person is able to effectively or adequately perform with an insufficient supply of oxygen. At altitudes below 30,000 feet, the time of useful consciousness (TUC) may differ considerably from the time of total consciousness.  Above 35,000 feet, actual times may be less than listed below.

The average TUC without supplementary oxygen is:

Note: Following an explosive decompression, the times listed above will be greatly reduced.

Flight attendant procedures in a decompression

Rapid or explosive

The immediate action for all crewmembers is to:

1. Grab the nearest mask and put it on.
2. Sit in the nearest seat and fasten the seatbelt, or sit on a passenger’s lap and order the passenger to tightly hold you.
3. Shout to passengers:

“NO SMOKING! PULL DOWN MASK! PUT ON! FASTEN SEATBELT! BREATHE NORMALLY!

The following actions are guidelines to follow until the aircraft lands:

1. To avoid interrupting essential communications between crewmembers in the flight deck, do not use the interphone until called by the flight crew.
2. Stay secured until the aircraft levels off and advised by the flight crew that the use of oxygen is no longer required. At that time it is safe to retrieve a Portable Oxygen Bottle and move around the cabin.
3. If a loss of cabin pressure occurs at night, all cabin lights should be turned on when able.

After advised it is safe to walk about the cabin, check the following in need of assistance:

1. Flight Deck crewmembers;
2. Other Flight Attendants;
3. Lavatories for passengers trapped inside and in need of oxygen;
4. Passengers throughout the cabin in need of oxygen or medical attention.

Warning: Make an announcement reminding all passengers must remain seated with their seatbelts fastened, and that smoking is prohibited at all times.

When the procedures have been accomplished to restore a safe cabin pressure altitude, the PIC will advise the Purser of the plan for conducting the remainder of the flight.

Insidious:

1. Keep in mind, a slow leak can become a rapid or explosive decompression at any time. Be prepared!  Prepare passengers. They should stay seated with seatbelts fastened.
2. If masks drop, FAs must react immediately! Pull down a mask wherever you are and command passengers to do the same.  Work your way through the cabin, mask to mask until you reach your jumpseat.  Notify the PIC once you are seated and secured.
3. If signs of hypoxia are visible, notify the PIC so cabin altitude and pressurization can be monitored.
4. Warn other crewmembers.
5. Be alert for further changes or instructions from the Flight Crew.
6. Secure galley and cabin areas if time permits.
7. Retrieve POB and don if needed.
8. Reseat passengers from the affected area if requested by the PIC, for example, if a window seal is leaking. Never stuff a blanket or other objects into a leak or door seal.

Hypoxia

As cabin crewmembers, it is important to understand and be familiar with the effects and symptoms of hypoxia which can result from a loss of cabin pressure. Hypoxia is a state of oxygen deficiency in the blood tissues and cells, sufficient to cause impairment of body function. The most important aspect to remember about hypoxia is that it can overcome a crewmember without obvious, definitive symptoms. Many of the symptoms associated with hypoxia can be mistaken for other ailments such as the flu, the common cold, or headache.  Usually, the first apparent symptoms of hypoxia are blurred vision, fatigue, and headache. The following are common symptoms associated with hypoxia:

• Increased breathing rate, headache, and fatigue.
• Light-headed or dizzy sensations and listlessness.
• Tingling or warm sensations and sweating.
• Poor coordination, impaired judgment.
• Distorted vision, sleepiness.
• Cyanosis (Discoloration of fingernail beds).
• Behavior changes, euphoria (feeling of well-being).

In addition to being aware of your own symptoms, it is also your responsibility to be aware of fellow crewmember’s and passenger’s behavior that may indicate the presence of hypoxia. If you suspect hypoxia in yourself, a fellow crewmember, or a passenger, this should be a warning signal to you that cabin pressure is being lost. Immediately notify the PIC!

Accidental passenger service unit mask drop

If the passenger oxygen masks deploy in flight:

• Notify the flight crew immediately.
• After assessing the situation, if no apparent problem with the aircraft, the flight will continue according to the PIC’s discretion.
• Passengers in the affected area should be reseated if possible.

If no other seats are available, brief the passenger:

• Do not touch or move the mask or it may activate the entire system.
• Should a decompression occur, pull the mask down until the tubing is fully extended to start the flow of oxygen.

Note: Do not attempt to repack the masks into the PSU.  Only Maintenance personnel are authorized to repack oxygen masks.