When dealing with hazardous materials - whether from a truck spill or a terrorist attack - information is critical. Before first responders can begin to aid victims and decontaminate a scene, they must determine what substances are present and understand the inherent risks to humans and the environment. To help first responders and hazardous materials (hazmat) teams, researchers at the Georgia Tech Research Institute (GTRI) have developed the Chemical Companion. This software tool, which operates on Windows CE-based personal digital assistants, provides detailed information on 130 of the most common chemicals associated with hazmat incidents. Sponsored by the federal government's Technical Support Work Group, the Chemical Companion helps first responders make decisions about protective equipment, chemical reactivity, isolation and protective zones and appropriate medical aid.