- Author
-
Gravatt, C. C.
- Title
- Light Scattering Methods for the Characterization of Particulate Matter in Real Time.
- Coporate
- National Bureau of Standards, Washington, DC
- Report
-
NBS SP 412,
October 1974,
- Book or Conf
- National Bureau of Standards and Food and Drug Administration. Aerosol Measurements: Proceedings of a Seminar. May 7, 1974,
Gaithersburg, MD,
Cassatt, W. A.; Maddock, R. S., Editors,
21-32 p.,
1974
- Keywords
-
aerosols
|
light scattering
|
smoke detectors
|
refractive index
- Identifiers
- aerosol sizing; aerosol spectrometer; chemical characterization of particles; particle size measurements; particulates refractive index
- Abstract
- This paper presents a brief overview of new light scattering methods for the rapid characterization of particulate matter in air. An instrument has been developed which determines the size distribuiton of particulate matter in air in esentially real time by a forward lobe light scattering method. The basic concept involves the simultaneous measurement of the intensity of light scattered by a single particle at two small scattering angles. The ratio of the two intensities is a direct measure of the size and is fairly independent of the index of refraction of the particle. Numerical solutions of the Mie equations for spheres have indicated that the sizing error by this method is not greater than ±15% for the range of particle sizes from 0.2 to 4 mum for essentially all possible indices of refraction. In addition, it appears feasible to extend the lower limit of size determination to 0.05 mum by the measurement of a single forward lobe intensity. Also, a technique has been developed which permits some degree of chemical characterization of particles, and which has been employed in a smoke detector capable of distinguishing between fire-produced and nonfire-produced aerosols.