PubMed · 543588
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J D Wood, J L Birkett. 1979. External airflow effects on personal sampling.. https://doi.org/10.1093/annhyg%2F22.3.299
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Several factors affecting breathing zone concentration were examined in a paint spray booth by using a tracer gas method. The variables in the study include contaminant momentum, the presence of a flat plate downstream of the worker, the distance between the contaminant source and the body, and the worker's motion. A dramatic reduction in breathing zone concentration was observed when the spray gun emitted contaminants with high momentum. Reductions of 30-50% were observed because of the other variables. The source momentum effect was studied, subsequently, in a wind tunnel by measuring the breathing zone concentration of a mannequin with various flows through jets of different diameter, at varying freestream velocities. A functional relationship was determined between nondimensional breathing zone concentration and contaminant source momentum. This relationship is supported by numerical simulations. The effect of contaminant momentum on the near-wake flow field is discussed in conjunction with results from the numerical simulations.
The purpose of this research was to determine the penetration of several filter materials commonly used in building air-handling systems by asbestos fibers. An airstream containing tremolite asbestos fibers was passed through these materials and the upstream and downstream fiber concentrations were measured by membrane filtration and scanning electron microscopy. The penetration of these materials was determined as a function of asbestos fiber diameter and length at two typical air velocities. For glass fiber filter materials, the maximum penetrations were 3.5% and 0.1% compared with American Society for Testing and Materials dust spot efficiency ratings of 80% and 90%, respectively. Thus, the glass fiber filters appear to be capable of greatly reducing the concentration of asbestos fibers in a building air-handling system. Roll and panel filter materials consisting of polyester fibers exhibited penetrations from 15% to nearly 90%. Thus, roll and panel filters tested are not recommended for this purpose.
The phenomenon of boundary layer separation can be an important factor in determining a worker's exposure to toxic airborne pollutants. A conceptual model was developed to understand this phenomenon and to predict the average concentration in the reverse flow region downstream of a worker in a uniform freestream. Subsequently, the assumptions of this model were tested experimentally in wind tunnel studies. On the basis of these results, a revised model is presented and validated by using a tracer gas method. The revised model provides a reasonable estimate of the average concentration in the reverse flow region of the mannequin. Empirical models are presented that relate both the average concentration in the reverse flow region and the breathing zone concentration to the body dimensions and the freestream air velocity. Applications and limitations of the results are discussed.