Which dispersion pattern describes the movement of the hazardous material by a responder?

• A. Pool
• B. Irregular
• C. Stream
• D. Hemispheric

Answer: (B)

Dispersion patterns describe how hazardous material spreads from its source and how actions in the environment influence that spread. When a responder moves through a release, their body, equipment, and the surrounding obstacles create turbulence and barriers that disrupt uniform spreading. This makes the material’s movement uneven, patchy, and unpredictable—what we call irregular dispersion.

A pool describes liquid spreading on a surface primarily by gravity and surface interactions, not by movement through the air. A stream implies a directed, coherent flow from a container. A hemispheric pattern is a roughly symmetrical cloud expanding in all directions in calm conditions. None of these fit the real effect of a responder moving through or around the release as well as irregular dispersion does.