Sodium oxide smoke detection in an enclosure - by transmitting polarised light through the enclosure, attenuation of the light indicating presence of the smoke

摘要

A source of light is polarized in a single plane and transmitted through the enclosure to a photodetector screened to receive only incident light having substantially the same angle of polarization as the light initially transmitted through the enclosure. Attenuation in the incident light below a given threshold is identified as being indicative of the presence of sodium oxide smoke within the gas enclosure. Alternatively, the photodetector is screened to receive incident light disorientated from the transmitted angle of polarization and an increase in the photodetector'a response will correspond to an increase in concn. of sodium oxide within the gas enclosure.