Classification of Poison Inhalation Hazard Materials Into Severity Groups*

Approximately 1.5 billion tons of hazardous materials (hazmat) are transported in the U.S. annually, and most reach their destinations safely. However, there are infrequent transportation accidents in which hazmat is released from its packaging. These accidental releases can potentially affect the health of the exposed population and damage the surrounding environment. Although these events are rare, they cause genuine public concern. Therefore, the U. S. Department of Transportation Research & Special Programs Administration (DOT-RSPA) has sponsored a project to evaluate the protection provided by the current bulk (defined as larger than 118 gallons) packagings used to transport materials that have been classified as Poison Inhalation Hazards (PIH) and recommend performance standards for these PIH packagings. This project was limited to evaluating bulk packagings larger than 2000 gallons. The goal of packaging performance standards is to ensure adequate public protection. One approach to setting performance standards is to select a cumulative percentage (X%) of accidents against which to protect the public, and a \"protection radius (R)\" around the accidental release beyond which the concentration of the released hazmat is below a chosen threshold value. The cumulative percentage of accidents correlates to specific accident conditions (i.e., X% of accidents have impact velocities less than or equal to a certain amount, thermal assault less than or equal to a certain amount, etc.) that the packaging must survive (Dennis et al. 1977). The package survives if, after experiencing the selected accident conditions, the hazmat release rate is small enough that the concentration at and beyond R is less than the chosen threshold level. This method defines a distance R beyond which people will not be exposed to concentrations in excess of the chosen threshold for (X%) of all accidents. This method does not describe the consequences of the (100- X)% of accidents that are more severe than the performance standard. However, if X is large, then the...