Time of useful consciousness
Time of useful consciousness (TUC), also effective performance time (EPT), is defined as the amount of time an individual is able to function effectively (e.g. perform flying duties) in an environment of inadequate oxygen supply.[1] It is the period of time from the interruption of the oxygen supply or exposure to an oxygen-poor environment to the time when useful function is lost, and the individual is no longer capable of taking proper corrective and protective action. It is not the time to total unconsciousness. At the higher altitudes, the TUC becomes very short; considering this danger, the emphasis is on prevention rather than cure.
For orbital altitudes and above, that is, direct exposure to space, 6–8 seconds of consciousness is expected.[2]
Medical analysis and variations
There are many individual variations of
The table below shows average TUCs as documented by the Federal Aviation Administration; a rapid ascent results in a lower TUC.[5] The TUCs for any given individual may differ significantly from this. Aerobic exercise during the TUC period will reduce the TUCs considerably; so will exercise immediately prior to the TUC as this induces an oxygen debt prior to exposure.[6]
Altitude (measured barometrically) | TUC (normal ascent) | TUC (rapid decompression) |
---|---|---|
FL180 (18,000 ft; 5,500 m) | 20 to 30 minutes | 10 to 15 minutes |
FL220 (22,000 ft; 6,700 m) | 10 minutes | 5 minutes |
FL250 (25,000 ft; 7,600 m) | 3 to 5 minutes | 1.5 to 3.5 minutes |
FL280 (28,000 ft; 8,550 m) | 2.5 to 3 minutes | 1.25 to 1.5 minutes |
FL300 (30,000 ft; 9,150 m) | 1 to 2 minutes | 30 to 60 seconds |
FL350 (35,000 ft; 10,650 m) | 30 secs to 1 minute | 15 to 30 seconds |
FL400 (40,000 ft; 12,200 m) | 15 to 20 seconds | 7 to 10 seconds |
FL430 (43,000 ft; 13,100 m) | 9 to 12 seconds | 5 to 6 seconds |
FL500 (50,000 ft; 15,250 m) | 8 to 10 seconds | 5 seconds |
See also
- Armstrong limit maximum survivable altitude
- Cabin pressurization
- Pressure suit
- Uncontrolled decompression
References
- ISBN 978-0-7817-2898-0.
- ^ Geoffrey A. Landis, Human Exposure to Vacuum web page
- PMID 10632134.
- PMID 9293349.
- ^ https://www.faa.gov/pilots/training/airman_education/media/AC%2061-107A.pdf [bare URL PDF]
- ^ Mark Wolff (2006-01-06). "Cabin Decompression and Hypoxia". theairlinepilots.com. Retrieved 2008-09-01.