Protecting the HVAC system from biological, chemical, and radiological weapons can be difficult. A paper by Michael MacDonald of Oak Ridge National Laboratory offers some guidance.The document helps security managers understand the various threats, pointing them to online sources for more detailed information. Also provided is an outline for performing vulnerability and threat assessments. In addition, the author explains how to reduce exposure to harmful agents and introduces readers to mitigation technologies and actions. The paper notes that no real-time biological sensor currently exists. Limited-efficacy chemical detectors and radiological sensors are available, but they are high in price.Also included is a fictitious case study that walks building managers through the process of securing a building’s HVAC system. Although targeted to managers in federal facilities, the guide is equally applicable to the private sector. Find the document online.