Patent ID: 6597288
Filing Date: 2003-07-22
Classification: G08B

Abstract:
A fire alarm system comprising:a smoke detector which detects a smoke density (S) in a target environment; a temperature detector which detects a temperature (T) of the target environment to give a temperature difference (&Dgr;T) within a predetermined time interval; threshold means for holding a plurality of primary criteria for determination of a fire presence, said primary criteria comprising: (i) whether the smoke density (S) exceeds a first smoke threshold (S1); (ii) whether the temperature difference (&Dgr;T) exceeds a first temperature difference threshold (TD1); and (iii) whether a combination of the smoke density (S) and the temperature difference (&Dgr;T) satisfies an inequality which is based upon a decreasing function of &Dgr;T with an increase of S; a controller which checks the detected temperature difference &Dgr;T and the detected smoke density S with reference to said primary criteria so as to provide a fire warning signal indicating a possible fire presence when anyone of the above primary criteria is satisfied.