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Effect Zone
The physical area in which a harmful effect is felt by a receptor. For a toxic release, the area over which the airborne concentration exceeds some level of concern. For a physical energy release, the area over which a specified overpressure criterion is exceeded. For thermal radiation effects, the area over which an effect based on a specified damage criterion [e.g., a circular effect zone surrounding a pool fire resulting from a flammable liquid spill, whose boundary is defined by the radial distance at which the radiative flux from the pool fire has decreased by 5 kW/m2 (approximately 1600 BTU/hr- ft2)].