People are major contributors of particle contamination in cleanrooms and therefore must wear occlusive clothing to reduce their dispersion. Three tests are described which assess the effectiveness of fabrics in filtering body emissions. Also described is a dispersal chamber in which the dispersal rate of a person can be ascertained.

Results from tests on a number of fabrics are given that demonstrate the ineffectiveness of many fabrics. The pore size dia of woven fabrics range from 17 to 103 μm and their removal efficiency against ⩾ 0.5 μm particles from a few percent to 75 percent. A comparison of clothing made from different fabrics in a dispersal chamber showed the close-woven fabrics and non-woven fabrics to be more effective. Fabrics with a low air permeability pumped out unfiltered body emission if care was not exercised in the design of the garment closures.

The greater importance of particles passing through fabrics compared to those coming off fabrics was demonstrated, as was the deterioration of fabrics through use. It was concluded that much of the clothing worn in cleanrooms could be greatly improved.

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