What is gas dispersion?
When a gas leak occurs, the gas tends to disperse into the atmosphere in a pattern based on its physical characteristics–its vapor density in particular. The diffusion rate of a gas into air is proportional to its density relative to that of air. Hydrogen, for example, with a density much lighter than air’s, will diffuse very rapidly. Because the resulting hydrogen-air mixture has a density lighter than the surrounding air, convection currents lift the mixture in a plume similar to smoke rising from a cigarette in an ashtray. For gases denser than air, the inverse is true. Most of the gases heavier than air are generated by liquids and are referred to as vapors. Gases with a density greater than air tend to settle along the ground or into a pit. Gases with densities very close to air do not diffuse much and tend to follow local air currents.
