National Institute for Occupational Safety and Health

“ Calculate the percentage of chrysotile in the bulk dust sample:
where: Îx = normalized intensity for sample peak b = intercept of calibration graph ( vs. W) m = slope of calibration graph (counts/μg) f (T) =
= absorption correction factor (Table 1)
R = sin ( T = Î Ag/ (average ) = transmittance of sample ÎAg = normalized silver peak intensity from sample average
= normalized silver peak intensity from media blanks (average of six
values) W = mass of deposited sample in μg. NOTE: For a more detailed discussion of the absorption correction procedure, see references [5] to [8] . ”

“ NIOSH Manual of Analytical Methods (NMAM) , Fourth Edition, 8/15/94 CHRYSOTILE ASBESTOS (BULK) : METHOD 9000, Issue 2, dated 15 August 1994 - Page 4 of 6 NOTE: A large intercept indicates an error in determining the background, i.e., an incorrect baseline has been calculated or interference by another phase. Select six silver membrane filters as media blanks (for determination of sample self-absorption, step 13) randomly from the same box of filters to be used for depositing the samples. ”

“ Normalizing to the reference specimen intensity compensates for long-term drift in X-ray tube intensity. If intensity measurements are stable, the reference specimen may be run less frequently; net intensities should be normalized to the most recently measured reference intensity. Determine the net count, I Ag, of an interference-free silver peak on the sample filter following the same procedure. ”