NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
ASBESTOS and OTHER FIBERS by PCM: METHOD 7400, Issue 2, dated 15 August 1994 - Page 11 of 15
The curves in Figure 1 are dened by the following equations:
and
,
where = subjective interlaboratory relative standard deviation, which is close to the total
interlaboratory when approximately 100 bers are counted,
= total bers counted on sample,
= lower 95% condence limit, and
= upper 95% condence limit.
Note that the range between these two limits represents 90% of the total range.
REFERENCES:
[1] Leidel, N. A., S. G. Bayer, R. D. Zumwalde, and K. A. Busch. USPHS/NIOSH Membrane Filter Method
for Evaluating Airborne Asbestos Fibers, U.S. Department of Health, Education, and Welfare, Publ.
(NIOSH) 79-127 (1979).
[2] Baron, P. A. and G. C. Pickford. “An Asbestos Sample Filter Clearing Procedure,” Appl. Ind. Hyg., 1,
169–171, 199 (1986).
[3] Occupational Safety and Health Administration, U.S. Department of Labor, Occupational Exposure
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Amended June 20, 1986.
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[9] Crawford, N. P., H. L. Thorpe, and W. Alexander. “A Comparison of the Eects of Dierent Counting
Rules and Aspect Ratios on the Level and Reproducibility of Asbestos Fiber Counts,” Part I: Eects
on Level (Report No. TM/82/23), Part II: Eects on Reproducibility (Report No. TM/82/24), Institute of
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[10] NIOSH Manual of Analytical Methods, 2nd ed., Vol. 1., P&CAM 239, U.S. Department of Health,
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[11] Revised Recommended Asbestos Standard, U.S. Department of Health, Education, and Welfare,
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[12] Asbestos International Association, AIA Health and Safety Recommended Technical Method #1
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(1989).
[14] “A Study of the Empirical Precision of Airborne Asbestos Concentration Measurements in the
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