Fire sensor systems effectively monitor the state of the building, detect fire, and alert occupants in the event of an emergency. However, fire sensor technology is limited in its ability to convey information to firefighters. Even though all of the necessary information can be obtained through Fire Annunciator Control Panels (FACPs), it is difficult to use them to track the progression of fire. We designed and prototyped a decision aid system to illustrate our approach to this problem. Our goal was to create a tactical decision aid display that can present building information through an intuitive interface in real time. We used previous research on the information needs of firefighters in designing the interface. Our key insight was to use a floor plan with a sensor information overlay to organize information. We implemented a prototype that interfaces with FACPs using existing facilities systems management communication protocols.