Abstract: A method of detecting a fire condition in a monitored region including the operations of: concurrently monitoring the region using: 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 fire combustion products, the plurality of fire combustion products equal to n; 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 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 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.

Abstract: A method of detecting a fire condition in a monitored region including the operations of: concurrently monitoring the region using: 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 fire combustion products, the plurality of fire combustion products equal to n; 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 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 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.

Abstract: A method of detecting the presence of a predetermined vapor of a predetermined concentration in a monitored area, the method including the steps of (a) exposing gas in or from the monitored area to radiation at wavelengths at least covering and surrounding from both sides a main absorption peak of the vapor; (b) simultaneously sensing the radiation after passing through the gas by a signal sensor and a reference sensor, each of the sensors including a radiation sensing element, wherein the signal sensor further includes a first optical filter passing wavelengths covering the main absorption peak, yet substantially blocking wavelengths from both sides of the main absorption peak of the vapor, whereas the reference sensor further includes a second optical filter passing wavelengths surrounding from both sides the main absorption peak, yet substantially blocking wavelengths covering the main absorption peak of the vapor; and (c) comparing signals obtained from the signal and reference sensors for determining a p