Because of the scale of contamination, gaseous fumigation with chlorine dioxide was proposed as the method of decontamination for the Senate building. However, because of the aggressive oxidizing nature of this gas, there was concern about the possible effects on artwork and sensitive technical equipment as well as personal items such as photographs in the building.
Tests of exposure to a number of quickly prepared test samples showed that damage such as fading of inks, dyes, and photographs did indeed occur . Mitigation of the problem by such techniques as surface treatment with oxidizing agents also was considered. In the end, the building was fumigated with chlorine dioxide after possibly sensitive or valuable objects and items were removed. These were treated separately by a number of methods appropriate to the types of objects, including chemical treatment and mechanical decontamination (HEPA vacuum cleaning).
Chemical treatments to mitigate biohazards include the traditional agents such as hypochlorite bleaches, peroxide based agents such as that developed at Sandia National Laboratories for chemical and biological warfare agents, and Oxone®, a DuPont product whose active ingredient is potassium peroxymonosulfate. The efficacy of each reagent depends on its concentration, method of application, and duration of exposure . For non-urgent situations, the time required for decontamination is not critical. In critical situations, however, effective action may be required in a relatively short time. For example, military guidelines generally require effective decontamination within one-half hour of application. The concentrations of the active agents in decontamination formulations generally are chosen so that they are effective in such a time frame. In the tests we conducted, we used standard concentrations and exposures of one-half hour in order to duplicate the types of exposure that might occur in practice.
This research was made possible through Grant MT-2210-02-NC-07 from the National Center for Preservation Technology and Training (NCPTT).