The Capitol Hill Site initially consisted of 26 buildings with suspected anthrax contamination. All 26 buildings were sampled; anthrax was detected in seven buildings, all of which were decontaminated and cleared for re-entry after confirmation sampling. Chlorine dioxide (ClO2) liquid, Sandia foam and high efficiency particulate arresting (HEPA) vacuums were used to decontaminate surfaces in office suites and mail handling areas. ClO2 gas was used to fumigate Senator Tom Daschle's suite and the heating, ventilation, and air-conditioning (HVAC) system inside the Hart Senate Office Building (Hart Building). Prior to decontamination, critical items were removed from the contaminated areas and transported off-site for sterilization using ethylene oxide (EtO) gas, after which they were returned to their respective owners.
The Capitol Hill Site response was different from most responses in terms of its size, complexity, and nature of contamination. The response involved the coordination of over 50 organizations and required a large amount of personnel and resources. This response was the first at which EPA was faced with anthrax contamination inside buildings; therefore, available decontamination technologies were limited.