In this paper, CFD techniques were applied to the simulations of hydrogen release from a 400-bar tank toambient through a Pressure Relieve Device (PRD) 6 mm ( ?) opening. The numerical simulations using theTOPAZ software developed by Sandia National Laboratory addressed the changes of pressure, density andflow rate variations at the leak orifice during release while the PHOENICS software package predictedextents of various hydrogen concentration envelopes as well as the velocities of gas mixture for thedispersion in the domain. The Abel-Noble equation of state (AN-EOS) was incorporated into the CFDmodel, implemented through the TOPAZ and PHOENICS software, to accurately predict the real gasproperties for hydrogen release and dispersion under high pressures. The numerical results were comparedwith those obtained from using the ideal gas law and it was found that the ideal gas law overestimates thehydrogen mass release rates by up to 35%2during the first 25 seconds of release. Based on the findings, theauthors recommend that a real gas equation of state be used for CFD predictions of high-pressure PRDreleases.