From the simulations performed using the ALOHA model, wind speed, atmospheric stability levels and total release time
have been identified as the primary causes for the discrepancies in the dispersion of toxic vapor between Scenario I and
Scenario II. Furthermore, from the results of dispersion in both seasons from both scenarios, with the exception of ERPG-1
level for epichlorohydrin dispersion in Scenario I and the IDLH and ERPG-2 levels for phosgene dispersion in Scenario II
having a discrepancy of 100 meters in the two scenarios, the data for other simulations showed insignificant differences.
From this, it would be safe to assume that the temperature had minor impact on the dispersion of the toxic substances in the
scenario simulations. Results of the scenario simulations for all three plants revealed that the release of phosgene at Plant C
had the greatest threat zone, followed by the release of chlorine at Plant A and the release of epichlorohydrin at Plant B. In a
hypothetical scenario where the source of phosgene release happened to be 500 meters downwind with phosgene
concentration reaching 0.3 ppm after an hour of release, one could deduce the rate of release to be at 37 kg/hr with an IDLH
area of 185 m. These simulation results could be used as the basis for relevant effects analysis and risk assessments. If
operators of petrochemical plants had performed the environmental survey at the initial stage of hazard and simulated the
pattern of toxic vapor dispersion using the ALOHA model by plugging in various measurements, the statistics from the
simulation would not only serve as a useful reference for the commanding officer of the rescue operation but also as a basis to notify residents in the affected areas to take necessary safety precautions to ensure the safety of their lives and properties