Measurements of the release of fission gases from spilled charcoal were made by means of a laboratory scale model developed for this study. It is shown that there is an appreciable retention of fission gases in charcoal and that the release rate can be determined from diffusion theory. For example, from a 1-ft-thick layer of spilled charcoal, it was found that 4.5% of the xenon and 21% of the krypton would be released after 6 h, and that 6.6 and 29%, respectively, would be released after 12 h. These results are in close agreement with the mathematical model developed for the analysis of these experiments. Similar release rates were found for spilled charcoal initially chilled to 0°F. These release rates are conservative because the effect of radioactive decay was neglected, and for this reason a theory was developed that includes the effect of radioactive decay within the spilled charcoal. The combined effects of a slow release rate and radiodecay will serve to mitigate the radiological consequences of a charcoal spill accident.