ASBESTOS REAL-TIME MONITOR IN AN ATMOSPHERIC-ENVIRONMENT

The concentration of asbestos fiber aerosols can be monitored by measu ring the polarization of laser light scattered by asbestos fibers. The principle of discriminating asbestos fibers is based on the theoretic ally expected difference in polarization at a scattering angle of 170 deg between cylindrical and spherical airborne particles; polarization at this scattering angle should be positive for cylindrical particles such as asbestos fibers but should be negative or close to zero for s pherical mineral particles. We constructed an experimental asbestos re al-time monitor that uses a strong electric field to align the airborn e particles, that uses lasers having Linear polarization with an equal amplitude in parallel and perpendicular components to the aligned lon g axis of particles, and that simultaneously detects the two component s of the Linear polarization of light scattered at 170 deg, i.e., clos e to the backscatter. Experiments that were performed to detect the li ght scattered from airborne standard asbestos fibers showed that the m easured polarization fits theoretical prediction. The concentrations o f airborne asbestos fibers obtained by the asbestos real-time monitor were consistent with those estimated by the standard phase contrast mi croscope method. (C) 1997 Optical Society of America.