[en] The equilibrium washout of tritiated water vapor (HTO) and tritium gas (HT) downwind from an instantaneous point source can be estimated by simple formulas. Derivations for three different models (Fickian Puff, Leaky Puff, and Leaky Garbage Can) are given for estimating the washout/m² from a puff. Two models are given (Leaky Garbage Can and Fickian Puff) for calculating the fraction of pollution remaining in a puff after it has traveled over an arbitrary distance. The relationship between washout and dry deposition problems is also discussed