Patent ID: 6377345
Filing Date: 2002-04-23
Classification: G08B

Abstract:
A particle detector for detecting particles of sizes of less than one micron, comprisingradiation emitting means for emitting radiation at two different wavelengths along a predetermined path through a scattering volume, the radiation at one of the wavelengths lying between about 400 mm and about 500 mm, the radiation of the other wavelength being infra-red radiation, radiation detecting means for receiving and detecting the radiation scattered from the scattering volume by the presence of particles at a predetermined forward scattering angle of less than 45Â° to the predetermined path of radiation, and output means for comparing outputs from the detecting means respectively corresponding to the received and detected radiation between about 400 nm and 500 nm and the received and detected infra-red radiation whereby to produce a warning signal when the comparison indicates that the particles are of a predetermined type but not to produce said warning signal when the comparison indicates that the particles are not of said predetermined type, the radiation at the two different wavelengths being simultaneously emitted along the predetermined path.