might not capture information quickly enough for fast-acting threat agents. LP-3 can be a fully automated detect-to-treat system and can also include human-in-the-loop decisions and actions to activate systems—that is, the sensor system notifies a person of a potential biological or chemical attack and the person takes action to minimize impact of the release. Thus, LP-3 might require training and sophisticated operational procedures to minimize human error. Another limitation of LP-3 and LP-4 is that active detection has the potential of falsely indicating the presence or absence of a threat.

LP-4 is a high-level active protection that can “detect to treat,” “detect to mitigate,” or “detect to warn and protect.” LP-4 includes rapid, automated systems. LP-4 eliminates the human decision factor, but the complex and sophisticated automated systems require routine maintenance to ensure their proper operation.

The relative risks of different levels of protection in the event of a biological or chemical attack depend on multiple factors. The fundamental risk underlying all levels of protection is the risk of exposing occupants to harm and disrupting building operations. One factor that influences this fundamental risk is the environment in which the protection system operates. If an active detection system (LP-3 or LP-4) operates in an environment with high background that causes either high false positives or negatives, an LP-3 or LP-4 system might not offer additional protection compared to an LP-2 system. The relative risks of different levels of protection can be assessed only in the context of the building in which the protection system operates.

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