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Protection of breathing zone by uniform velocity blowing.

A system of work site ventilation that blows clean air around a worker's nose and mouth was studied. The characteristics of the blowing flow were examined experimentally and then for a practical application. Field tests were performed to confirm the effectiveness of the blowing equipment during concrete chipping at a building construction site. This type of ventilation was found to be useful for contaminants with relatively low toxicity (e.g., nuisance dust); however, the technique may increase the exposure of workers in adjacent areas, since the dust is not captured or filtered. It became evident that the worker's dust exposure during the chipping could be decreased by using the air-blowing equipment.