Manhattan Experiments Track Gases For Terror Response

Last Monday, scientists from several government agencies released two tracer gases in a 2-km 2 area of midtown Manhattan. In a series of experiments, they are tracking how harmful gases or particles might disperse through street canyons, subway tunnels, and buildings. Dubbed the Urban Dispersion Project, this Department of Homeland Security-sponsored effort aims to produce a computer model of airflow patterns that could help state and local officials better respond to an emergency or to a biological or chemical terrorist act. On six days over a three-week period ending Aug. 26, sulfur hexafluoride and perfluorocarbons are to be released from three open-air sites within the designated area. Some 200 samplers will monitor the gases as they ride the wind. The monitors are positioned on streetlight poles, on rooftops, on subway platforms, and within an office building. In addition, 15 to 20 people equipped with personal sampling devices will walk the affected ...