Interim NIOSH Training for Emergency Responders: Reducing Risks Associated with Long Work Hours

Be Alert for Key Factors that Promote Fatigue-Related Errors and Injuries

Time of day (circadian effect)

  • The strongest dip in wakefulness occurs between about 2 a.m. and 6 a.m.
  • The second most vulnerable times are between 2 to 5 p.m. and from midnight to 2 a.m.

Time awake and amount of sleep

  • The longer you have been awake, the greater your risk for fatigue
  • Poor quality and short duration of recent sleep (buildup of sleep debt) puts you at greater risk for fatigue
  • Avoid building up sleep debt

Time on task

  • The longer the time you spend on a task, particularly one that is monotonous, the more likely you will feel fatigue.
  • Take rest breaks
  • Change the task or conditions

If two or three factors occur at the same time, the risks of poor performance due to fatigue are higher. Remember when you are sleep deprived, you are particularly vulnerable to errors during the middle of the afternoon and at night.

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Page last reviewed: April 1, 2020