Now that environmental awareness is enhanced on a global basis, great hopes are placed on the expanded use of hydrogen stations and fuel-cell vehicles (FCVs) that economize hydrogen energy. Hydrogen stations must be safe and secure because they store large quantities of hydrogen under higher pressure than the hydrogen actually consumed by FCVs. Thus, multiple safety measures are taken to ensure that hydrogen does not leak from the stations. Furthermore, in the unlikely event of leakage, the damage needs to be kept on an allowable level. For this reason, it is necessary to understand the behavior of hydrogen gas leaking from the stations. It is well known that hydrogen is a highly explosive gas, being combustible over a wide range of concentrations. Due to this property of hydrogen, tests for verifying its behavior must be done outdoors. In the open air, however, tests are affected by weather conditions and hydrogen sensors' responses are delayed, which makes it difficult to observe an accurate distribution of hydrogen concentrations. Therefore, with respect to assumed cases of hydrogen leakage, a concentration distribution of hydrogen gas was obtained by means of computational fluid dynamics (CFD). The analysis results were used for verifying the safety of hydrogen stations. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.