All of the links below will cause you to exit the Federal Executive Board's website.
However, the information is provided as a collection of useful resources that we hope will be helpful to you in designing your plan for Sheltering-in-Place.
CDC - Chemical Agents: Facts about Sheltering in Place
http://www.bt.cdc.gov/planning/shelteringfacts.asp
Homeland Security: Shelter In Place
http://www.nationalterroralert.com/shelterinplace/
Homeland Security: Every Business Should Have a Plan
http://www.ready.gov/business/_downloads/ReadyBusinessBrochure.pdf
Advice for Safeguarding Buildings: Pre-Event - Establish internal "safe zones"
http://securebuildings.lbl.gov/PA_LT_Zones.html
Advice for Safeguarding Buildings Against Chemical or Biological Attack: Outdoor Release
http://securebuildings.lbl.gov/outdoor.html
Advice for Safeguarding Buildings Against Chemical or Biological Attack: Indoor Release
http://securebuildings.lbl.gov/indoor.html
Secure Buildings: Response to an Indoor Chemical or Biological Attack - HVAC information
http://securebuildings.lbl.gov/images/fr_advice_s.pdf