Factors affecting the design of local exhaust ventilation for the control of contaminants from hand-held sources.
Appl Occup Environ Hyg 1990 Oct; 5(10):707-714
The tracer gas concentration in the breathing zone of a mannequin from a small hand held point source in front of exhaust hood was examined as a function of specific basic design parameters. Flanged circular hoods used in this study were 10.2, 22.9 and 30.5 centimeters in diameter. Sulfur-hexafluoride was used as a tracer. The results suggested that the orientation of the worker with respect to the hood and the source is an important variable in determining the concentration in the breathing zone. When the worker is involved with a low momentum, hand held source of pollution, positioning the body 90 degrees to the centerline offered superior protection to the standard 180 degree orientation. This orientation effect was the single most significant factor in controlling exposure observed in this study. These results argued for active training in work practices in conjunction with well designed engineering controls. The authors recommend that the 90 degree position be investigated as the preferred orientation in all situations involving local exhaust hoods with hand held sources. The observation that exposure increases with proximity of the small hood at a fixed flow suggests more complicated aerodynamics are at work than can be addressed with the standard capture velocity approach.
NIOSH-Publication; NIOSH-Grant; Control-technology; Work-practices; Ventilation-systems; Exhaust-hoods; Ventilation-hoods; Exhaust-ventilation
Environmental Sciences & Engr University of North Carolina Rosenau Hall 201H Chapel Hill, NC 27514
Applied Occupational and Environmental Hygiene
University of North Carolina Chapel Hill, Chapel Hill, North Carolina