User Defined Releases define concentric circles of risk which can be useful for hazards such as BLEVEs or confined explosions (for example, regions surrounded by walls and a roof which generate overpressure).
A frequency for the user defined release along with up to three consequence distances and corresponding vulnerabilities is required.
High distances must be smaller than medium distances which in turn must be smaller than low distances. High vulnerabilities must be higher than medium vulnerabilities which in turn must be higher than low vulnerabilities.
