Northeast Utilities Service Company

Richard G Stafford

Richard Kounai Chang

A system and method for monitoring the concentration of micron size pollutants in a gas, such as sulphate aerosols in the ambient air. The gas is drawn through a dichotomous sampler which segregates the larger aerosols from the smaller ones. The smaller sized particles of aerosols are concentrated and then flowed through an inspection chamber having a plurality of optical windows. The sample is illuminated by the light beam from a laser, and a plurality of mirrors provide a light trap to redirect the laser radiation to the sample a large number of times. The Raman scattered radiation from the particles is collected by a mirror and by a lens onto a spectrograph which provides spectrally dispersed radiation according to the molecular constituents of the sample. This radiation is detected and converted to electrical signals providing qualitative and quantitative information as to the pollutant composition and concentration.

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New Haven, CT, United States of America

Richard G Stafford