In-depth survey report: control technology for environmental enclosures - the effect of wind speed upon aerosol penetration into an enclosure at Clean Air Filter, Defiance, Iowa, report no. CT-223-15a.
NIOSH 1999 Feb; :1-20
The effect of wind speed upon aerosol penetration into an idealized enclosure was studied. The idealized enclosure was a painted plywood box that was 1.2X1.2 X1 meters in volume. Two fans supplied 1.7 (cum)/min of filtered air to this enclosure at a static pressure of 2.8 mm of water. The enclosure had a 7.5 cm diameter vent port which was isolated from the air flow around the enclosure. To simulate holes in real enclosures, three 1.6-cm diameter holes were drilled on the front and back sides of the enclosure. This simulated enclosure was placed in a tunnel-like structure. The air flow from an ultra-light aircraft was directed at the front of the enclosure. The air speeds were varied between 14 and 26 km/hr as measured by rotating vane anemometer. Static pressure in the enclosure was measured with an electronic manometer. Two optical particle counters measured the particle number concentration of particles between the 0.35 to 0.5 um inside and outside of the enclosure. Aerosol penetration into the enclosure was computed as the ratio of the aerosol concentration inside the enclosure to the concentration outside of the enclosure. Aerosol penetration into the enclosure was computed as the ratio of the aerosol concentrations inside the enclosure to the concentration outside of the enclose. The enclosure static pressures measured increase form 2.8 to 3.4 mm of water (P=0.0001). Aerosol penetration into the enclosure increased linearly with air velocity about the simulated enclose. When simple linear regression was used to model the observed penetration as a function of the estimated penetration, the value of the slope was 0.69 +/- 0.12 and the P value for the regression model was less than 0.0001. These results indicate that enclosure static pressure needs to be higher than the wind's velocity pressure in order to minimize aerosol penetration into these enclosures.
Air-flow; Region-8; Aerosols; Analytical-processes; Analytical-methods; Sampling-equipment; Sampling-methods
Field Studies; Control Technology
NTIS Accession No.
National Institute for Occupational Safety and Health