ASBESTOS and OTHER FIBERS by PCM: METHOD 7400, Issue 2, dated 15 August 1994 - Page 12 of 15
[15] McCrone, W., L. McCrone and J. Delly, “Polarized Light Microscopy,” Ann Arbor Science (1978). [16] Ogden, T. L. “The Reproducibility of Fiber Counts,” Health and Safety Executive Research Paper 18 (1982). [17] Schlecht, P. C. and S. A. Schulman. “Performance of Asbestos Fiber Counting Laboratories in the NIOSH Proficiency Analytical Testing (PAT) Program,” Am. Ind. Hyg. Assoc. J., 47, 259–266 (1986). [18] Chatfield, E. J. Measurement of Asbestos Fiber Concentrations in Workplace Atmospheres, Royal Commission on Matters of Health and Safety Arising from the Use of Asbestos in Ontario, Study No. 9, 180 Dundas Street West, 22nd Floor, Toronto, Ontario, CANADA M5G 1Z8. [19] Walton, W. H. “The Nature, Hazards, and Assessment of Occupational Exposure to Airborne Asbestos Dust: A Review,” Ann. Occup. Hyg., 25, 115–247 (1982). [20] Cherrie, J., A.D. Jones, and A.M. Johnston. “The Influence of Fiber Density on the Assessment of Fiber Concentration Using the membrane filter Method.” Am. Ind. Hyg. Assoc. J., 47(8), 465–74 (1986). [21] Baron, P. A. and S. Shulman. “Evaluation of the Magiscan Image Analyzer for Asbestos Fiber Counting.” Am. Ind. Hyg. Assoc. J., (in press). [22] Taylor, D. G., P. A. Baron, S. A. Shulman and J. W. Carter. “Identification and Counting of Asbestos Fibers,” Am. Ind. Hyg. Assoc. J. 45(2), 84–88 (1984). [23] “Potential Health Hazards of Video Display Terminals,” NIOSH Research Report, June 1981. [24] “Reference Methods for Measuring Airborne Man-Made Mineral Fibers (MMMF),” WHO/EURO Technical Committee for Monitoring an Evaluating Airborne MMMF, World Health Organization, Copenhagen (1985). [25] Criteria for a Recommended Standard…Occupational Exposure to Fibrous Glass, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-152 (1977). METHOD WRITTEN BY: Paul A. Baron, Ph.D., NIOSH/DPSE. APPENDIX A. CALIBRATION OF THE WALTON-BECKETT GRATICULE Before ordering the Walton-Beckett graticule, the following calibration must be done to obtain a counting area ( ) 100 µm in diameter at the image plane. The diameter, (mm), of the circular counting area and the disc diameter must be specified when ordering the graticule. 1. Insert any available graticule into the eyepiece and focus so that the graticule lines are sharp and clear. 2. Set the appropriate interpupillary distance and, if applicable, reset the binocular head adjustment so that the magnification remains constant. 3. Install the 40 to 45× phase objective. 4. Place a stage micrometer on the microscope object stage and focus the microscope on the graduated lines. 5. Measure the magnified grid length of the graticule, (µm), using the stage micrometer. 6. Remove the graticule from the microscope and measure its actual grid length, (mm). This can best be accomplished by using a stage fitted with verniers. 7. Calculate the circle diameter, (mm), for the Walton-Beckett graticule: . Example: If = 112 µm, = 4.5 mm, and = 100 µm, then = 4.02 mm. 8. Check the field diameter, (acceptable range 100 µm ± 2 µm) with a stage micrometer upon receipt of the graticule from the manufacturer. Determine field area (acceptable range 0.00754 mm² to 0.00817 mm²).
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
