5-2 Neutrally Buoyant Dispersion Models
Neutrally buoyant dispersion models are used to estimate the concentrations downwind of a
release in which the gas is mixed with fresh air to the point that the resulting mixture is neutrally
buoyant. Thus these models apply to gases at low concentrations, typically in the parts per
million range.
Two types of neutrally buoyant vapor cloud dispersion models are commonly used: the
plume and the puff models. The plume model describes the steady-state concentration of material
released from a continuous source. The puff model describes the temporal concentration
of material from a single release of a fixed amount of material. The distinction between the two models is shown graphically in Figures 5-1 and 5-2