The development of hydrogen as energy carrier is promoted by the increasing in energy demand, depletion of fossil resources and the global warming. However, this issue relies primarily on the safety aspect which requires the knowledge, in the case of gas release, of the quantities such as the flammable cloud size, release path and the location of the lower flammability limit of the mixture. The integral models for predicting the atmospheric dispersion were extensively used in previous works for low pressure releases such as pollutant and flammable gas transport. In the present investigation, this approach is extended to the high pressure gas releases. The model is developed in the non-Boussinesq approximation and is based on Gaussian profiles for buoyant variable density jet or plume in stratifed atmosphere with a crossflow. Validations have been performed on a broad range of hydrogen, methane and air disp ersion cases including vertical or horizontal jets or plumes into a quiescent atmosphere or with crosswind.