United States Nuclear Regulatory Commission - Protecting People and the Environment
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Derived Air Concentration-Hour (DAC-hour)

The product of the concentration of radioactive material in air (expressed as a fraction or multiple of the derived air concentration for each radionuclide) and the time of exposure to that radionuclide, in hours. A licensee may take 2,000 DAC-hours to represent one annual limit on intake (ALI), equivalent to a committed effective dose equivalent of 5 rems (0.05 Sv).

Page Last Reviewed/Updated Wednesday, May 07, 2014