Recent events have increased awareness of the risk posed by terrorist attacks. Bacillus anthracis has resurfaced in the 21st century as a deadly agent of bioterrorism because of its potential for causing massive civilian casualties. This analysis presents the results of a computer simulation of the dispersion of anthrax spores in a typical 50-story, high-rise building after an intentional release during a bioterrorist incident. The model simulates aerosol dispersion in the case of intensive, small-scale convection, which equalizes the concentration of anthrax spores over the building volume. The model can be used to predict the time interval required for spore dispersion throughout a building after a terrorist attack in a high-rise building. The analysis reveals that an aerosol release of even a relatively small volume of anthrax spores during a terrorist incident has the potential to quickly distribute concentrations that are infectious throughout the building.

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Analysis of the dispersion of malignant anthrax spores in a 50-story tower block after a terrorist act has been carried out. A computer model of the aerosol dispersion in the case of intensive small-scale convection equalizing the concentration of malignant anthrax spores in separate rooms of the building has been developed. The model permits predicting the time interval needed for the spores to disperse. It has been shown that the release of even a relatively small amount of malignant anthrax spores can lead to a dangerous contamination of the whole building.The application of agents of biological weapons for committing a terrorist act jeopardizes public safety. As a biological weapon, many microorganisms that cause dangerous diseases or produce toxins (i.e., viruses, bacteria, fungus spores, etc.) can be used. Soil microorganisms Bacillus anthracis, whose metal protease is the cause of the dangerous disease known as "malignant anthrax," have been identified as a probable bacteriological threat. The etiological agent of malignant anthrax is a rather large gram-positive bacterium having the form of a rod. Spores of size 1-5 µm effectively penetrate into the lungs. Investigations on primates have shown that 3-5 spores can initiate an infection. Eight thousand spores are enough to cause the death of a human if no therapeutic intervention had been used before the process of exotoxin formation began. When spores are inhaled and get into the organism, bacilli multiply rapidly and, as a result, bacteria and toxins get into the human circulatory system [1]. Before the advent of antibiotics (1938), inhaling malignant anthrax was very dangerous. Even at the present time its danger is still rather high. For instance, for patients who had not begun treatment before signs of strong intoxication appeared, mortality during the American epidemic in 2001 was 45% [2].Because of their virulence and elasticity, malignant anthrax spores are extremely attractive as bioterrorist agents, since they can easily be obtained both under laboratory conditions and from natural sources. Grown and purified spores are very small particles that are absorbed with a high probability in human alveolae. Spores can be released into the atmosphere with the help of various devices, including the simplest devices for powder sputtering [3].The spreading of malignant anthrax spores by mail that took place in the United States of America in October-November of 2001 demonstrated that the bioterrorist threat may become reality. The analysis carried out in the present paper permits estimating the dispersion and the inhaling dose of malignant anthrax spores after a terrorist act in a 50-story tower block.Methodology. The computer model used is based on ideas first presented in [4], where the dispersion of spores was described for the case of intensive small-scale convection that equalizes their concentration in the premises of the building. The time interval needed for removing suspended spores from the building was estimated from the point of view of a multich...