Slow , or gradual , decompression occurs slowly enough to go unnoticed and might only be detected by instruments . This type of decompression may also come about from a failure to pressurize as an aircraft climbs to altitude . An example of this is the 2005 Helios Airways Flight 522 crash , in which the pilots failed to check the aircraft was pressurising automatically and then to react to the warnings that the aircraft was depressurising , eventually losing consciousness ( along with most of the passengers and crew ) from hypoxia
Helios Airways Flight 522
Helios Airways Flight 522
Uncontrolled decompression