The H2 concentration was measured in the ventilated air of actual high-level liquid waste tanks of the Tokai reprocessing plant. It was compared with the value calculated from the parameters that were obtained using the simulated solution. Both values agreed satisfactorily within the limits of uncertainties of the parameters. This agreement showed that the catalytic H2 consumption reaction caused by Pd ions, which was found previously using the simulated solution, proceeds also in the actual solution. The measured “G(H2)” for the actual solution and the derived one using the parameters from the simulated solution were between 7×10−6 and 3×10−5.