||Destruction of Spores on Building Decontamination Residue in a Commercial Autoclave.
Sieber, R. ;
Osborne, A. ;
Lemieux, P. ;
||Eastern Research Group, Inc., Chantilly, MA. ;Environmental Protection Agency, Research Triangle Park, NC. National Homeland Security Research Center.
Biological weapons ;
Building decontamination residue ;
Ceiling tiles ;
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In the event of a terrorist attack on a building where biological weapons such as anthrax might be used, much of the porous material in the building will be shipped for disposal after decontamination activities. This material is collectively termed 'building decontamination residue' (BDR). Although the BDR will have been disinfected or decontaminated, it is possible that residual biological agent will remain in the material. Autoclaves are commonly used to sterilize regulated medical waste by exposing the waste to elevated pressures and temperatures for extended periods of time (e.g., 31.5 psig, 275 deg F, and 40 minutes). However, some types of BDR may be densely packed or have low thermal conductivity and may require longer periods of time to reach the operating temperature of an autoclave. This report addresses whether the standard operating procedure in a commercial autoclave will provide sufficient time/temperature/pressure to adequately destroy bacteria spores bound on BDR. This study investigated the effect of several variables related to autoclaving BDR, including time, temperature, pressure, item type, moisture content, packing density, packing orientation, autoclave bag integrity, and autoclave process sequence. The test team created simulated BDR from wallboard, ceiling tiles, carpet, and upholstered furniture, embedded with 10(sup 6) population Geobacillus stearothermophilus biological indicator (BI) strips and thermocouples to obtain time/temperature profile data associated with each BI strip. Study results indicate that bags of BDR should be placed in an autoclave so that all sides of individual bags are exposed to autoclave conditions, and not nested or stacked in a manner that precludes full exposure. All materials tested were effectively sterilized when dry. Increasing moisture content made autoclaving more difficult, but wet wallboard and ceiling tiles were also effectively sterilized. Autoclave cycles of 120 minutes at 31.5 psig/ 275 deg F and 75
minutes at 45 psig/ 292 deg F effectively sterilized the BDR material. Two standard autoclave cycles of 40 minutes and 31.5 psig/ 275 deg F run in sequence proved to be particularly effective, probably because the second cycle's evacuation step pulled the condensed water out of the pores of the materials, allowing effective steam penetration.
||Prepared in cooperation with Environmental Protection Agency, Research Triangle Park, NC. National Homeland Security Research Center.
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