The Department of Homeland Security’s (DHS) Chemical Security Analysis Center (CSAC), which is part of the Science and Technology branch, has issued a Request for Information (RFI) seeking sources to execute a gap analysis for atmospheric transport and dispersion modeling of large-scale toxic chemical releases. There is a concern and evidence that current modeling and consequence assessment approaches are inadequate at addressing large-scale releases of some toxic chemicals. The CSAC is tasked with identifying the relevant knowledge and capability gaps and making recommendations to enable improvement of these methodologies. Sol. No. RFI-ST-TD-09-01. Respond by Dec. 12. In a separate but related RFI, CSAC is seeking sources to execute a systems assessment and develop the experimental plan to determine the effect of chemical reactions on Toxic Inhalation Hazard (TIH) material concentration in vapor and aerosol clouds. The removal or conversion of TIH materials to different chemicals via reactions in the environment can have a significant impact on the concentration of the material present or its toxic effects. However, the experimental data necessary to appropriately account for these reactions in current models is scarce or nonexistent for most TIH materials of concern. Sol. No. RFI-ST-TD-09-02. Respond by Jan. 2, 2009. Contact: Timothy Davis, contracting officer, 202-254-5676, [email protected].