Patent ID: 7638770

Claim:
A method of detecting a fire condition in a monitored region including the operations of: (a) concurrently monitoring the region using: (i) a single detector having a plurality of fire combustion product emission band sensors, each band sensor sensitive to radiation within a respective waveband which includes at least part of a respective fire combustion product emission band of a plurality of non-identical fire combustion products, the plurality of non-identical fire combustion products equal to n; (ii) a first reference band sensor sensitive to radiation within a first reference waveband which includes at least some wavelengths shorter than the n fire combustion product emission bands; and (iii) a second reference band sensor sensitive to radiation within a second reference waveband which includes at least some wavelengths longer than the n fire combustion product emission bands; and (b) using the band sensors to obtain n+2 measurement values of radiation intensity emitted from the monitored region in determining the presence or absence of the fire condition wherein the n+2 measurement values include: n measurement values obtained from the emission band sensors; one measurement value obtained from the first reference band sensor; and one measurement value obtained from the second reference band sensor and from which detection parameters are calculated, which are evaluated against at least one threshold in determining the presence or absence of the fire condition wherein the detection parameters include two respective reference ratios calculated for each of the n measurement values: a first reference ratio between respective n measurement values and the measurement value from the first reference band sensor; and a second reference ratio between respective n measurement values and the measurement value from the second reference band sensor.