Positron annihilation spectroscopy was used to investigate the temperature, time and pressure dependence of the equilibration of the thermal vacancy concentration in B2-Fe61Al39 after fast temperature changes at elevated temperatures. A two stage equilibration process was observed with a migration enthalpy of H-V(1)M = (0.8 +/- 0.2) eV and H-V(2)M = (1.7 +/- 0.3) eV for a faster, initial process and a long-term, main process, respectively. For the main process a formation volume of V-V(F) = (1.5 +/- 0.3) Omega and a migration volume Of V-V(F) = (4.6 +/- 1.1) Omega for thermal vacancies were determined. By employing coincident Doppler broadening studies it could be demonstrated for the first time for the model case of FeAl that thermal vacancies are formed on the transition metal sublattice.