People detect danger by relating many observations to one another and comparing them to familiar patterns. The simultaneous use of multiple senses allow humans to filter out situations which are not dangerous. The ability to detect danger depends largely on intelligence and knowledge from past experience. Kidde 4D detectors provide both. The GSA-IPHS Intelligent 4D Multisensor Detector gathers analog information from each of its three fire sensing elements (ionization, photoelectric, and heat) and converts it into digital signals. The detector’s on-board microprocessor measures and analyzes these signals separately with respect to a fourth element - Time. We call this technology 4D. It compares the information to historical read- ings, time patterns and several known fire characteristics to make an alarm decision. Digital filters remove signal patterns that are not typical of fires. Unwanted alarms are virtually eliminated.