The natural and forced mixing and dispersion of hydrogen released in an accidental manner in a partially enclosed compartment with vents at multiple heights is investigated using theoretical tools. The key to the analysis is determination of the position of the neutral buoyancy plane, where the pressure in the compartment is equal to that of the exterior. Air flows in through vents below the position of neutral buoyancy and exits from vents above it. CFD simulations are conducted to confirm the physical phenomena and to compare with the analytical results. The analytical model is useful in understanding the important physical processes involved during hydrogen release and dispersion in a compartment with vents at multiple levels, with and without a steady wind. Parametric studies are conducted to identify the relative importance of various parameters. Model results indicate that the steady-state hydrogen volume fraction in the compartment is lower when the hydrogen release rate is smaller and the vent cross-sectional area is larger. Results also indicate that the fastest way to reduce flammable levels of hydrogen concentration in a compartment can be accomplished by blowing through the vents. Published by Elsevier Ltd on behalf of Professor T. Nejat Veziroglu.