Abstract Tritium (hydrogen) accumulation and release processes at MnS precipitates and surrounding αFe matrix area at room temperature (RT) were studied by means of tritium autoradiography (TARG) using a pseudo-binary alloy of Fe–MnS. Hydrogen accumulation at the MnS precipitates at RT was clearly observed but only at a limited occasion. The process involves diffusion, solution and trapping in a complex way including a temperature effect. TARG is proved to be a very good technique to obtain hydrogen area profiles in a near surface region, whereas it is only a snap shot at a particular time and temperature. It could lead us to a totally different interpretation of the accumulation process without detailed dependencies of hydrogen diffusivity and solubility in inclusion species and αFe on temperatures.