We develop and apply an integrated modeling system to estimate fatalities from intentional release of 17 tons of chlorine from a tank truck in a generic urban area. A public response model specifies locations and actions of the populace. A chemical source term model predicts initial
characteristics of the chlorine vapor and aerosol cloud. An atmospheric dispersion model predicts cloud spreading and movement. A building air exchange model simulates movement of chlorine from outdoors into buildings at each location. A dose‐response model translates chlorine exposures
into predicted fatalities. Important parameters outside defender control include wind speed, atmospheric stability class, amount of chlorine released, and dose‐response model parameters. Without fast and effective defense response, with 2.5 m/sec wind and stability class F, we estimate
approximately 4,000 (half within ∼10 minutes) to 30,000 fatalities (half within ∼20 minutes), depending on dose‐response model. Although we assume 7% of the population was outdoors, they represent 60–90% of fatalities. Changing weather conditions result in approximately
50–90% lower total fatalities. Measures such as sheltering in place, evacuation, and use of security barriers and cryogenic storage can reduce fatalities, sometimes by 50% or more, depending on response speed and other factors.