Modern facility design have engineered out many failure events caused by the failure of a single component or equipment unit. Therefore, a key key goal of these simulations is to capture emission events which occur 275 when two or more rare failures occur simultaneously. For example, in modern facilities with three or more stages of separation process, small amounts of gas flash during the last separation stage before liquid storage tanks. If the separator's dump valve sticks open, the tank's control system (typically a combustor) is likely to handle all of the incoming gas. However, if both valve and flare fail simultaneously, emissions may be substantial and caught by aerial or on-site surveys.