Analysis of a series of urban-scale chlorine dispersion experiments and implications on indoor health consequences

In the United States, industrial compounds are routinely transported by rail in pressurized vessels, often near urban areas. A rupture of a vessel, for example due to a derailment, can result in the rapid release of a liquid-aerosol-gas mixture. The health consequences of such a release, especially close to population centers, are not well understood. To address this question, a series of controlled experimental releases of pressurized chlorine (Cl₂) was conducted at the Dugway Proving Ground (Dugway, Utah). Each trial consisted of the sudden breach of a tank containing at least 4,500 kg (kg) of pressurized liquid Cl₂. In this paper, we report on measured Cl₂ concentrations in three test structures downwind of the release. Based on these data, we estimate the indoor-outdoor exchange, transport through a multi-room structure, and the first-order loss rate due to reaction or sorption. This loss rate is particularly important for consequence assessment. For example, in a mobile office with a ventilation rate of about three air changes per hour, the reaction loss rate was approximately 2.5 h⁻¹. This accounts for a nearly 20 percent reduction in toxic load to indoor occupants. Finally, the paper discusses the modeling and analysis of a typical urban hazard assessment.