FIRE DETECTION USING CROSS-CORRELATIONS OF SENSOR SIGNALS

Experiments have been carried out to investigate the efficacy of signal cross-correlation techniques to provide early detection of fire. Cross-correlations were of the form <A . B> and <A . B . C>, where A, B and C were signals from various sensors and < > denotes averages of signal products over a correlation time interval, tau(C), extending from present time into the past. All signals were referenced to their baseline averages extending over a time interval, tau(B), into the past. Tests were conducted in a room, quiescent or highly ventilated, using fire sources modeled on the test fires of European Standard EN54. Various sensors responded to airborne pyrolysis and combustion products. Two complementary cross-correlations, <DELTA-CO . DELTA-ION> and <DELTA-CO2 . DELTA-T>, were shown (with tau(B) selected in the range 100-250 s and tau(C) selected in the range 10-25 s) to be equivalent to a much more sensitive detection system than implied by the limits of the most sensitive EN54 class, where DELTA-CO and DELTA-CO2 are referenced carbon monoxide and carbon dioxide concentrations, DELTA-ION is the referenced output of a measuring ionization chamber, and DELTA-T is the referenced temperature.