Security personnel (i.e., guards) potentially risk occupational exposures to hazardous substances including chemical, biological, radiological, and nuclear (CBRN) materials during emergencies. Emergencies involving the release of hazardous chemicals at industrial facilities, including chemical manufacturers and industrial facilities utilizing hazardous substances, are the most likely and predictable incidents that may involve security personnel. Security personnel, however, work at a variety of locations with the potential for emergency incidents. Although general chemical release emergencies may be the most likely, incidents resulting from natural disasters or involving weapons of mass destruction (WMD) are also of concern to both private and public sector employers and the security personnel they employ. Security personnel working at companies for the protection of the facilities, materials, and products, as well as those employed by government agencies, are often called upon to provide support during hazardous substance emergencies and the emergency planning in preparation for such incidents is key to successful implementation of emergency response operations. This document specifically addresses emergencies involving hazardous substance releases and provides guidance for employers, and their security personnel, who may be involved in the emergency response. It does not address other safety and health hazards (e.g., workplace violence) that security personnel may be exposed to while performing their routine duties.