- Author
- Chen, D. R.
- Title
- Detecting Particulates in Real-Time: Optical Techniques.
- Coporate
- Washington Univ., St. Louis, MO
- Report
- NIST SP 1051; NIST Special Publication 1051, December 2007,
- Book or Conf
- Real-Time Particulate Monitoring: Detecting Respiratory Threats for First Responders. Workshop Proceedings. Appendix 3: Workshop Presentations. Appendix 3.E. May 3-4, 2007, Gaithersburg, MD, 49-53 p., 2007
- Keywords
- first responders | respiratory systems | health hazards | fire fighters | particulates | reflectance | diffraction | lasers | photometers | particle size distribution
- Identifiers
- incident light beam; refraction
- Abstract
- Optical techniques for detecting particulates take advantage of the changes to an incident light beam caused by interaction with particles. Refraction, reflection and diffraction are the three types of elastic scattering mechanisnls, which redirect the incident beam without changing its wavelength. Refraction is the bending of light within a particle; reflection redirects the light from the particle surface; and diffraction bends light external to the particle. Diffraction works best for large particles. Single particle detection requires the sensing volume to be small compared to the inverse of the particle number concenttation. Detectors using this method count individual particles and may measure particle size distribution. Multiple particle detectiorl works for larger sensing volumes. Photometers are simple, inexpensive, and robust but need to be carefully calibrated. For measurernents of mass, the accuracy depends on the particulate size distribution.