A risk reduction scheme for exposure to an accidental release of a dense gas from a transportation accident

The purpose of this study is to determine the effects on indoor environments of an accidental release of a hazardous gas from a transportation-related incident, using a newly developed algorithm that combines dense gas and indoor air modeling components. A risk reduction scheme to reduce indoor exposure to accidental releases is developed which is based on the indoor air exposure calculated from modeling release scenarios involving the quantities of material released, the time of day of the release, and the community types where the release occurs. The release simulations involve eight chemicals, all of which are transported as pressurized liquids. The risk reduction scheme incorporates areas of (1) immediate evacuation and (2) indoor sheltering with subsequent evacuation, along with a response index that provides a method of communicating the proper response activities. The scheme developed here may be used by emergency response personnel to protect individuals in homes and other structures that may be affected by dense gas accidental releases.; The modeling results provide valuable information on limits of the amounts that should be transported as well as time of day restrictions for hazardous material shipments by highway. Based on the results of this study, some of the chemicals should not be transported under nighttime conditions in large quantities because they produce dense vapor clouds that, even at low concentrations, can cause harmful concentrations to buildup indoors. If shipment of these chemicals must occur at night, then smaller quantities are recommended to reduce the potentially large effect that a release could have on nearby communities.