System and method of smoke detection using multiple wavelengths of light and multiple sensors

Abstract

In accordance with certain embodiments, detection of a fire event via detection of scattered light of at least two wavelengths is initiated only after a signal from a light detector and/or a sensor for detecting one or more fire signatures other than smoke exceeds a triggering threshold.

What is claimed is: 
     
         1 .- 31 . (canceled) 
     
     
         32 . A smoke detector comprising:
 a housing;   one or more light emitters for emitting, to a sampling volume within and/or outside of the housing, light of a first wavelength and a second wavelength longer than the first wavelength;   one or more light detectors positioned to detect light emitted from the one or more light emitters scattered by smoke particles in the sampling volume back to the one or more light detectors, thereby providing measurements of scattered light including the first and second wavelengths;   one or more sensors for detecting one or more fire signatures other than smoke; and   an evaluation circuit for (i) comparing an output of at least one light detector and/or at least one sensor to a threshold and, (ii) only when the threshold is exceeded, determining the presence of smoke particles within the sampling volume based on (a) a measurement of scattered light including the first wavelength and (b) a measurement of scattered light including the second wavelength.   
     
     
         33 . The smoke detector of  claim 32 , wherein:
 the one or more sensors comprises an ambient light sensor;   the evaluation circuit is configured to (i) correct a measurement of scattered light including the first wavelength based on the detected ambient light level, thereby producing a corrected first-wavelength measurement, (ii) correct a measurement of scattered light including the second wavelength based on the detected ambient light level, thereby producing a corrected second-wavelength measurement, and (iii) determine the presence of smoke particles within the sampling volume based on a ratio or a difference of the corrected first-wavelength measurement to the corrected second-wavelength measurement.   
     
     
         34 . The smoke detector of  claim 32 , wherein the one or more sensors comprise an ambient light sensor. 
     
     
         35 . The smoke detector of  claim 32 , wherein the one or more sensors comprise a heat sensor. 
     
     
         36 . The smoke detector of  claim 32 , wherein the one or more sensors comprise a humidity sensor. 
     
     
         37 . The smoke detector of  claim 32 , wherein the one or more sensors comprise a gas sensor. 
     
     
         38 . The smoke detector of  claim 32 , wherein the one or more sensors comprise a sound sensor. 
     
     
         39 . The smoke detector of  claim 32 , wherein the sampling volume is disposed outside of the housing. 
     
     
         40 . The smoke detector of  claim 32 , wherein the sampling volume is disposed within the housing. 
     
     
         41 . The smoke detector of  claim 32 , wherein:
 the one or more sensors comprises an ambient light sensor;   the evaluation circuit is configured to (i) compare the output of the ambient light sensor to the threshold, and (ii) signal that the threshold is exceeded when the output of the ambient light sensor comprises a characteristic signature of a flicker of a fire.   
     
     
         42 . The smoke detector of  claim 41 , wherein the characteristic signature of the flicker of a fire has a frequency ranging from approximately 1 Hz to approximately 20 Hz. 
     
     
         43 . The smoke detector of  claim 32 , wherein the evaluation circuit is configured to (i) compare the output of at least one light detector to a first threshold, (ii) compare the output of at least one sensor to a second threshold, and (iii) determine the presence of smoke particles within the sampling volume only when both the first and second thresholds are exceeded. 
     
     
         44 . The smoke detector of  claim 32 , wherein the evaluation circuit is configured to determine the presence of smoke particles within the sampling volume by comparing, to a second threshold, a value based at least in part on at least one of (i) the measurement of scattered light including the first wavelength, (ii) the measurement of scattered light including the second wavelength, (iii) a sum of the measurement of scattered light including the first wavelength and the measurement of scattered light including the second wavelength, (iv) a difference between the measurement of scattered light including the first wavelength and the measurement of scattered light including the second wavelength, or (v) a ratio of the measurement of scattered light including the first wavelength and the measurement of scattered light including the second wavelength.