Document re6eLb3aZjvv065XBna5OeJVr

September 26, 2372 PLAINTIFFS EXHIBIT - CHV-127 MEMO TO TF 110.^ ASBESTOS: S. L. Dryden talked with Bon Ott, Industrial Hygienist for the local OSEA Region today in order to clarify the monitoring requirements for asbestos under OSEA (29 CFR 1910.93a). The standard merely states that samples are to be analyzed by "the membrane filter method at 1+00-45CK.. .with phase contrast illumination." Ko reference is made to aiy guideline document. OSEA uses Appendix I of the HIOSH Criteria Document (CD) aa their guideline, but it carries no legal clout. My specific questions related to the number of fields (or fibers) which must be counted and the minimum sampling time for statistical validity. The CD recommends inspecting as many fields as are necessary to count at least 100 fibers (generally 20 to 100 fields). Mr. Ott indicated that the counting procedure is a matter of professional judgement and following the CD is not essential for compliance with the monitoring requirements of the standard. In terms of sampling short-term operations, Mr. Ott felt that the wording of the standard ("Ho employee shall be exposed any- time to airborne concentrations.... .in excess of 10 fibers/ce..") precludes the use of the CD recommendation of a 15 minimum sampling time for operations that take less than 15 minutes. That is, the sampling period should approximate the length of exposure in short-term operations, and additional sampling time which would dilute the sample cannot be tacked on. cc: R. W. Adex* S. L. DHXDEN