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The effect of wind speed upon aerosol penetration into an enclosure.

Authors
Heitbrink-W; Thimons-E; Organiscak-J; Cecala-A
Source
American Industrial Hygiene Conference and Exposition, May 20-25, 2000, Orlando, Florida. Fairfax, VA: American Industrial Hygiene Association, 2000 May; :48
NIOSHTIC No.
20041456
Abstract
Environmental enclosures are used on vehicles used in agriculture, construction, and surface mining to protect the operator from exposure to air contaminants such as pesticides and respirable crystalline silica. A recent ASAE standard (S525) specifies an enclosure static pressure of at least 6 mm of water. This specification was based on professional judgment rather than data. Application of Bernoulli's equation indicates that air infiltration through holes occurs when the enclosure static pressure is less than the wind's velocity pressure. To test this hypothesis, the effect of wind speed on aerosol penetration into an idealized enclosure was studied. The idealized enclosure was a plywood box, 1.2 m x 1.2 m x 1 m in volume. Two fans supplied 1.7 m3/min of filtered air to this enclosure at a static pressure of 2.8 mm of water. The enclosure had three 1.6 cm diameter holes in the front and a 7.5 cm diameter vent port that was isolated from the airflow around the enclosure. The airflow from an ultralight aircraft was directed at the front of the enclosure to simulate wind. The air speeds were varied between 14 km/hr and 36 km/hr, as measured by a rotating vane anemometer. An electronic manometer measured the static pressure in the enclosure. Two optical particle counters measured the particle number concentration of particles between 0.35 microm and 0.5 microm inside and outside the enclosure. Aerosol penetration into the enclosure was computed as the ratio of the aerosol concentration inside the enclosure to the concentration outside the enclosure. Aerosol penetration into the enclosure and cabin static pressure increased linearly with air velocity above 20 km/hr. 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 (p < 0.0001).
Keywords
Air-contamination; Air-flow; Air-pressure; Air-monitoring; Particle-aerodynamics; Standards; Aerosols; Environmental-contamination; Environmental-technology; Environmental-control-equipment; Filtration; Pressure-gradients; Testing-equipment; Simulation-methods; Particle-accelerators; Particle-counters; Mathematical-models
Publication Date
20000520
Document Type
Abstract
Fiscal Year
2000
NTIS Accession No.
NTIS Price
NIOSH Division
DPSE; PRL
Source Name
American Industrial Hygiene Conference and Exposition, May 20-25, 2000, Orlando, Florida
State
OH; PA; FL; VA
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