US EPA

3658807 

Journal Article 

Uniformity of Particle Deposition for Indoor Air Sampling under Anisokinetic Conditions 

Fletcher, RA; Steel, EB; Beard, M; Wang, CC; Gentry, JW 

1989 

Yes 

Journal of Aerosol Science
ISSN: 0021-8502
EISSN: 1879-1964 

NIOSH/00195313 

20 

8 

1593-1596 

Studies of the uniformity of particle deposition for indoor air sampling occurring under anisokinetic conditions were summarized. The studies utilized a wind tunnel having a 0.51 by 0.91 meter cross section to simulate an indoor environment during an asbestos (1332214) abatement project and were designed to determine the effects of wind velocity, particle size, sample orientation, and face velocity upon the filter and sampling efficiency. Twenty five millimeter graphite impregnated filter cassettes were exposed to test aerosols consisting of 2 micron monodisperse fluorescein particles that moved at velocities of 0.15 to 0.68 meter per second (m/s). The cassettes were oriented at one of three angles with respect to wind direction, 0 degrees facing into the flow stream, 45 degrees downward, or 90 degrees upward. After exposure, the filters were removed and the fluorescein particles were counted by a fluorescence microscope. In some experiments the filters were extracted with ethanolic ammonia and the fluorescein was determined spectrophotometrically. A 17.5 by 17.5 centimeter (cm) region located 30.5cm from the top and 40.6cm from the right side of the tunnel contained a relatively uniform and particle rich region. At wind and face velocities of 0.2m/s deposition of the particles on the filters was generally uniform at all orientations. At a wind velocity of 0.2m/s and a face velocity of 0.5m/s slight oversampling and undersampling occurred when the filter cassettes were oriented 45 degrees downward. The authors conclude that there seems to be some nonideal behavior in sampling efficiency as a function of cassette orientation when sampling at higher face velocities.