This announcement does not request any proposals at this time. Requests for Proposals (or Calls) will be accomplished via amendments to this BAA. The over-arching strategy of this BAA involves the use of this 3.5-year Open BAA(OBAA) to quickly and efficiently execute research and development to deliver practical solutions to urgent chemical and biological defense priorities. This strategy will provide DHS an acquisition tool with the flexibility to solicit proposals and make awards to perform rapid prototyping of technical solutions to meet present and compelling chemical and biological defense needs, as ever-changing urgent operational issues and capability gaps are identified. The BAA will remain "open" for 3.5 years; however, proposals will only be solicited and accepted during calls. Each call will identify topics and contain a common cut-off date for proposal submission. Proposals received after the specified due date and time shall be governed by the provisions of FAR 52.215-1(c)(3). Calls for proposals (made by amendments to this BAA) will occur periodically throughout the life of this over-arching BAA. Each call will: (1) identify specific topic areas; (2) identify any changes to the standard evaluation criteria or proposal preparation instructions, and; (3) contain common cutoff dates for proposal submissions.