Characteristics of Aerosol Penetration through Seams
Date Issued
2014
Date
2014
Author(s)
Wu, Nian-Cih
Abstract
Personal protective clothing is designed to protect workers against hazardous substances that might come into contact with the skin. Several test methods have been developed to measure barrier properties of particulate protective clothing (PPC) against particulate assaults, normally in terms of total inward leakage. However, it has been shown that PPC provided less protection when the junctions became part of the ensemble. Those officially accepted test methods might not be appropriate to identify and characterize the leakage through junctions. Therefore, this study aimed to investigate the characteristics of aerosol penetration through junctions, mainly seams.
The main objective of this study was to develop two test methods for evaluating the aerosol penetration through particulate protective clothing materials: (1) Active sampling method: monitoring aerosol penetration through PPC under extremely low filtration velocity, and (2) Closed-return sampling train method: using a closed-return to measure the PPC performance without active sampling. The active sampling method is useful to illustrate the aerosol penetration through protective clothing, when the wearers are in motion, vacuum might be created inside the clothing. The closed return sampling train method simulated the relative velocity due to indoor air flow and/or wear’s moving.
In order to cover a broad size range, a constant output atomizer and an ultrasonic atomizing nozzle were used to generate polydisperse sub-micrometer-sized and micrometer-sized particles, respectively. The aerosol output was neutralized by using a 25 mCi radioactive source, Am-241, and then introduced into the mixing (test) chamber. Two different particle size spectrometers were used to measure the aerosol concentrations and size distributions upstream and downstream of the filters: a scanning mobility particle sizer (SMPS) for particles smaller than 0.7 mm, and an aerodynamic particle sizer (APS) for particles larger than 0.7 mm.
Both active sampling method and closed return sampling train method showed that the aerosol penetration through clothing with seam was much higher than that of clothing without seam. This phenomenon was particularly significant when the air resistance of clothing material was high. Sewing method also influenced PPC performance. Serge seam with twin top stitches was superior to simple serge seam. Pressure drop across clothing with seam decreased with increasing needle size. Aerosol penetration through clothing with seam was depended on needle size. A particular needle with coarser yarn helped reduce aerosol penetration, especially for high air resistance material, e.g. Tyvek.
Subjects
微粒穿透率
微粒防護衣
車縫邊
主動式採樣系統
內循環系統
Type
thesis
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