The principal developmental focus of the LIMIT code is the ability to model hydrogen transport accurately in reactor containments. The program is capable of treating rapid two-phase dominated blowdown transients, slower mixing events in which diffusional transport is important, and lumped or nodal multicompartment analysis. The code’s features include versatile multidimensional geometry options and models of ancillary equipment including solid heat sinks and mass and energy sources. The program is applied to a number of pertinent problems including continuum analysis of a hydrogen/water blowdown, simulation of experimental tests performed at the Battelle-Frankfurt Institute and the Hanford Engineering Development Laboratory, and lumped parameter studies of connected room problems. The code is shown to be capable of accurately treating a wide range of problems with reasonable computational efficiency. The need for even better efficiency, additional equipment submodels, and further validation are the code’s principal limitations.