Derived Air Concentration-Hour (DAC-Hour) Law and Legal Definition
According to 10 CFR 20.1003 [Title 10 – Energy; Chapter I -- Nuclear Regulatory Commission; Part 20 -- Standards for Protection Against Radiation; Subpart A -- General Provisions], the term derived air concentration-hour (DAC-hour) “is 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 ALI, equivalent to a committed effective dose equivalent of 5 rems (0.05 Sv).”
