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Sampling Biases Associated with In-Facepiece Sampling.

Water Engineering Research Laboratory, U.S. Environmental Protection Agency, Cincinnati, Ohio, 1985 Dec:224 pages
Efforts were undertaken to determine whether variations in specific parameters of the person/respirator system could cause systematic bias in measurements of concentration made with in/facepiece sampling techniques. The concentration inside the facepiece as a result of faceseal leakage was theoretically estimated; experimental verification was sought. Small, medium and large faceseal leakages on the MSA full facepiece were associated with sampling biases of - 31, -35 and -40 percent, respectively. No significant difference between leak rates was indicated by analysis of variance. Duncan's Multiple Range Test indicated that the 40 percent sampling bias measured with large leak rates was significantly worse than the bias introduced with the other two leak rates. Using the Scott Number 1 full facepiece, sampling biases with small, medium and large leaks were -14, -29 and -30 percent, respectively. Data on the Scott Number 2 full facepiece was markedly different with small, medium and large leak rates causing sampling biases of 14, 15 and 12 percent, respectively. Using the U.S. Divers full facepiece gave a sampling bias associated with small and medium leakages of 10 percent. However, with the large leakage the bias was -1 percent. The author concludes that faceseal leakage is streamlined within the facepiece cavity of the respirator during each period of inhalation. Positions of these streamlines relative to the sampling probe appear to be the major cause of observed sampling bias.
Respiratory-protection; Personal-protective-equipment; Respirators; Sampling-equipment; Sampling-methods; Personal-protection; Protective-equipment;
Publication Date
Fiscal Year
NTIS Accession No.
NTIS Price
Priority Area
Control Technology and Personal Protective Equipment; Research Tools and Approaches; Respirator Research; Respirators;
Source Name
Water Engineering Research Laboratory, U.S. Environmental Protection Agency, Cincinnati, Ohio, 224 pages, 64 references