A novel technique for performing in-air d( 3He, p) nuclear reaction analysis of deuterium using external 3He ion beams ranging in energy from 0.3–2.0 MeV is presented. Variable on-target beam energies for the depth profiling of deuterium are obtained by varying the transmission distance of the external 3He beam in air. The ex-vacuo nuclear reaction analysis (XNRA) apparatus is described, and unique aspects and limitations of in-air depth profiling of deuterium using the d( 3He, p) reaction are discussed. Example analyses where XNRA has been used for the multidimensional measurement of deuterium in fusion reactor components are presented in order to illustrate the advantages of XNRA for deuterium. These advantages include nondestructive analysis of large targets, efficient depth profiling via variable air gap energy tuning, and rapid analysis of numerous samples in the absence of vacuum cycling.