Key airborne concentrations of chemicals for emergency response planning in HAZMAT road transportation- margin of safety or survival

The release of chemicals due to road transportation accidents could have adverse consequences such as fatality, physical and financial loss and environmental damage. The purpose of this study was to determine the suitable margin of safety/survival of individuals in HAZMAT road transportation accidents for use in Emergency Response Planning (ERP). In this study, at first, the safety margin and survival margin were defined and proposed. Then, as a case study, the chemical tanker trucks in Iran's road transport fleet were investigated and the full bore rupture of the tanker trucks was considered as the selective scenario. Eventually, safety margin and survival margin were determined using ALOHA and PHAST software and the Chemical Exposure Index (CEI). The results showed that using the CEI, among the selected chemicals, ammonia, chlorine and 1,3-butadiene had the highest chemical release potential with the exposure indices of 597, 548 and 284, respectively, and need further investigation. The possible safety margin obtained in this study was distances over 5100 m (using ALOHA software for ammonia) and 10,983 m (using PHAST software for chlorine). On the other hand, the survival margin was distances over 980 m away from the accident area (using ALOHA software for ammonia) and 620 m away from the accident area (using the PHAST software for chlorine). The results of this study indicate that determining the safety and survival margins surrounding the tanker trucks and containers of chemicals is a critical issue for the emergency response planning and determining the standards of road's safety and survival margins. On the other hand, due to the obtainment of different results by various methods and software, in road accidents, the highest hazard distance is suggested to be considered to determine the safety margin (distances longer than 10,983 m) and survival margin (distances longer than 980 m) for ERP, regardless of the type of used material and software.