Abstract: An intelligent fire detection system is disclosed which includes a control panel and a plurality of detectors distributed throughout the building being protected. The software of the panel treats the detectors as being in one or more groups. All the detectors in a group can be in the same room. The detectors are set so as to be sensitive to small concentrations of smoke eg 0.3% per meter obscuration. Only if all the detectors in a group, or a predetermined lesser number of the detectors in a group, have smoke concentrations at or above the threshold level does the panel establish an alarm condition. The panel can also establish an alarm condition when the presence in any single detector of smoke at a higher concentration eg 3% per meter obscuration is detected. The system can alternatively include detectors sensitive to other emissions from a fire eg heat, ionized particles or carbon monoxide.