Definition

The Time of Useful Conciousness (TUC) or Effective Performance Time is the period of elapsed time from the interruption of normal air supply or exposure to an oxygen-poor environment until the time when the ability to function usefully is likely to be lost, at which point an affected individual would no longer be capable of taking normal corrective or protective action.

Time of useful consciousness (TUC) is not the time to total unconsciousness.