ASBESTOS and OTHER FIBERS by PCM: METHOD 7400, Issue 2, dated 15 August 1994 - Page 3 of 15
EQUIPMENT (continued): 10. Acetone flash vaporization system for clearing filters on glass slides (see ref. [5] for specifications or see manufacturer’s instructions for equivalent devices). 11. Micropipets or syringes, 5-µL and 100- to 500-µL. 12. Microscope, positive phase (dark) contrast, with green or blue filter, adjustable field iris, 8 to 10× eyepiece, and 40 to 45× phase objective (total magnification ca. 400×); numerical aperture = 0.65 to 0.75. 13. Graticule, Walton-Beckett type with 100-µm diameter circular field (area = 0.00785 mm²) at the specimen plane (Type G-22). Available from Optometrics USA, P.O. Box 699, Ayer, MA 01432 [phone (508)-772-1700], and McCrone Accessories and Components, 850 Pasquinelli Drive, Westmont, IL 60559 [phone (312) 887-7100]. NOTE: The graticule is custom-made for each microscope. (see APPENDIX A for the custom-ordering procedure). 14. HSE/NPL phase contrast test slide, Mark II. Available from Optometrics USA (address above). 15. Telescope, ocular phase-ring centering. 16. Stage micrometer (0.01-mm divisions). SPECIAL PRECAUTIONS: Acetone is extremely flammable. Take precautions not to ignite it. Heating of acetone in volumes greater than 1 mL must be done in a ventilated laboratory fume hood using a flameless, spark-free heat source. SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. To reduce contamination and to hold the cassette tightly together, seal the crease between the cassette base and the cowl with a shrink band or light colored adhesive tape. For personal sampling, fasten the (uncapped) open-face cassette to the worker’s lapel. The open face should be oriented downward. NOTE: The cowl should be electrically grounded during area sampling, especially under conditions of low relative humidity. Use a hose clamp to secure one end of the wire (Equipment, Item 3) to the monitor’s cowl. Connect the other end to an earth ground (i.e., cold water pipe). 3. Submit at least two field blanks (or 10% of the total samples, whichever is greater) for each set of samples. Handle field blanks in a manner representative of actual handling of associated samples in the set. Open field blank cassettes at the same time as other cassettes just prior to sampling. Store top covers and cassettes in a clean area (e.g., a closed bag or box) with the top covers from the sampling cassettes during the sampling period. 4. Sample at 0.5 L/min or greater [6]. Adjust sampling flow rate, (L/min), and time, t (min), to produce a fiber density, , of 100 to 1300 fibers/mm² (3.85×10⁴ to 5×10⁵ fibers per 25-mm filter with effective
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
