To assess the risk and determine the parameters of the event, performance or spreading of the emergency situations, specialized computer software is used, by initiating specific values for the type of hazardous substances, equipment, weather conditions.
The program ALOHA (Aerial Locations of Hazardous Atmospheres) is developed jointly by the Department for assessment and preparedness for accidents involving hazardous substances by the U.S. administration for oceanic and atmospheric research and offices for emergency preparedness and prevention activities of the Agency for Environmental Protection (EPA) of USA. The program is used mainly for creating models of dispersion of volatile substances.
Certain advantages and disadvantages in software ALOHA are exposed below.
includes models of gases with density close to that of air, and a model for heavier than air gases;
presents in graphic form the dispersion distribution of the gas as a dependence of the concentration and the distance from the site of leakage;
enables to choose measurement units with which data is entered and results are received from the calculations;
library holds more than 700 substances and products;
accounts the concentration changes depending on the distance of open spaces and enclosed spaces;
in two-phase (gas and aerosols) leakage from the tank of liquefied gas into, the program accounts the cooling of the tank due to evaporation of the liquid and the change in the rate of leakage;
does not account for the concentration change in height, gives values for the concentration of ground atmospheric layers;
results about velocity dispersion of cloud move in time are not displayed, the amendment of the concentration in a specific point in the direction of the wind, respectively;