Risk analysis evaluates the risk of individual hazard scenarios and hazardous events that contribute to the overall risk of a hazardous facility. Therefore, some practitioners employ risk tolerance criteria for hazard scenarios or hazardous events by allocating or apportioning overall facility risk to the scenarios or events. Issues encountered in allocating facility risk tolerance criteria are discussed in this article, including estimating the number of scenarios or events to which a person may be exposed, introducing uncertainty into risk tolerance criteria, and defining scenarios or events uniquely and equivalently. Recommendations are made for using risk tolerance criteria appropriately. (c) 2013 American Institute of Chemical Engineers