Staying Safe during an Aircraft Depressurisation: Passenger Information Bulletin


Aircraft depressurisation events are rare, but they can occur with little or no warning. The faster you put on your oxygen mask, the better the chance that you will stay safe and remain capable of helping children and others. Reading this safety bulletin will help ensure that you can recognise and appropriately react to an aircraft depressurisation if one should occur.

Why are aircraft pressurised?

Modern aircraft are designed to fly at high altitudes. (For example, large jet aircraft normally cruise at an altitude of 28,000 – 35,000 ft). This is because aircraft consume less fuel and can fly in relatively smooth air, avoiding bad weather and turbulence. However, the human body is not designed to survive at such high altitudes so the
air pressure inside the cabin needs to be controlled.

The air pressure inside the cabin cannot be kept the same as the ambient air pressure at ground level as doing so would put excessive stress on the aircraft. Therefore, air pressure altitude inside the cabin (as measured by the equivalent outside altitude) gradually rises from takeoff to a maximum of 8,000 ft during the cruise. During the descent to the destination airport, the cabin pressure altitude is gradually reduced to match the ambient air pressure of the airport. Without a fully functional pressurised cabin, passengers and crew need to use oxygen systems at the altitudes typically attained during cruise.

What is depressurisation?

Depressurisation, also called decompression, is the reduction of atmospheric pressure inside a contained space such as the cabin of a pressurised aircraft.


Type: Safety Education Material
Investigation number: AR-2008-075
Publication date: 12 December 2008
ISBN: 978-1-921490-92-7
Publication number: AR-2008-075(1)
Related: Cabin Safety
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