SCATTERED RADIATION FIRE DETECTOR AND METHOD FOR THE AUTOMATIC DETECTION OF A FIRE SITUATION

The invention relates in particular to a scattered radiation fire detector (1) having radiation sources (2, 3) of different wavelengths and a scattered radiation sensor (4), which are arranged and formed so that their optical axes (9, 10) are directed at a common centre of a scattering volume (5). A sensor unit is furthermore formed in order to register forward scattering I1(.lambda.1,fwd) of a first radiation source (2), forward scattering I2(.lambda.2,fwd) of a second radiation source (3) and backward scattering I3(.lambda.1,bwd) of a further first radiation source (2), to calculate scattered radiation intensity quotients Q1 = I1(.lambda.1,fwd)/I2(.lambda.2, fwd), Q2 = I1 (.lambda.1,fwd)/I3(.lambda.,bwd) and Q3 = I2(.lambda.2,fwd)/I3(.lambda.1,bwd) and in order to use them for the decision regarding the existence of a fire situation.