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Reopening Public Facilities after a Biological Attack: A Decision Making Framework
Technical questions—simple and complex—about a variety of issues, such as what to do with wastewater from worker decontamination baths and where to place testing apparatus during the decontamination process, must be answered.
The actual decontamination operation of a building is likely to be conducted in a few days, although the schedule depends on the size of the project and its complexity. Temperature, relative humidity, concentration of decontamination agent, and contact time typically must be measured and recorded during decontamination. The success of the operation, however, and the avoidance of major technical or public relations problems, will largely depend on the quality of the planning.
Two strategies can be used to verify successful decontamination. If the contaminant has been physically removed, for example by high efficiency particulate air (HEPA) vacuuming, verification will need to rely on the second method. If the contaminant has been left in place but inactivated, then environmental sampling after the decontamination is the most direct testing method. Direct validation of procedures that remove the contaminant is difficult. Direct validation is the demonstration that signatures of the original organism are still present—as determined by antibody binding or DNA hybridization assays—but that the samples are culture negative. The presence of actual target organisms in a place where samples are collected cannot be confirmed in the absence of such data. A culture test, in the absence of signature validation, cannot defend against the challenge that a collection was culture negative only because the collection process missed the target organisms. Results can be compared with those obtained before the procedure and against the standard specified as being “clean enough” to warrant a halt to further decontamination. A detailed sampling plan should be in place beforehand, including specific locations to be sampled, so that results will be useful and significant once they are known.
A second strategy for validation is the use of surrogate organisms, or spore strips with defined numbers of spores on each strip. The test strips are placed in various locations before remediation and tested for viability afterward. That validation is best suited for fumigants and not appropriate for liquid preparations (Box 10-1).
Although the committee was not asked to recommend specific methods for decontamination, the four steps listed here are so intertwined that the committee could not reasonably deal with assessment, planning, and verification without also considering decontamination. Moreover, the committee hopes that this report will be helpful to any facility manager who must cope with biological contamination. The discussion of decontamination methods presented here should provide a summary of the issues involved in choosing an approach.
Decontamination methods can be classified into three categories—vapor-phase treatment, reactive-solution treatment, and physical decontamination. Many