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ASBESTOS by TEM: METHOD 7402, Issue 2, dated 15 August 1994 -Page 3 of 7 SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. For personal sampling, fasten sampler to worker's lapel near worker's mouth_ Remove the top cover from cowl extension ("open-face") and orient sampler face down. Wrap joint between extender and monitor body with tape to help hold the cassette together and provide a marking surface to identify the cassette. Where possible, especially at low%RH, attach sampler to electrical ground to reduce electrostatic effects during sampling. 3. Submit at least two field blanks (or 10% of the total samples, whichever is greater) for each set of samples. Remove top covers from.the field blank cassettes and store top covers and cassettes in a dean area (e.g., dosed bag or box) during sampling. Replace top coGers when sampling is completed. 4. Sample at 0.5 to 16 Umin [3]. Adjust sampling rate, Q (Umin), and time, t (min), to produce fiber density, E. of 100 to 1300 fibers/mm Z [3.85 - 10` to 5 • 105 fibers per 25-mm filter with effective collection area (A 385 mm 2)] for optimum accuracy_ Do not exceed ca. 0.5 mg total dust loading on the filter. These variables are related to the action level (one-half the current standard), L (fibers/cc). of the fibrous aerosol being sampled by: A, E t = , flllft. Q - L 1Q3 NOTE: The purpose of adjusting sampling times is to obtain optimum fiber loading on the filter. A sampling rate of 1 to 4 Umin for 8 h (700 to 2800 L) is appropriate in atmospheres containing ca. 0.1 fiber/cc in the absence of significant amounts of non-asbestos dust. Dusty atmospheres require smaller sample volumes ( <_400 L) to obtain countable �N samples. in such cases take short, consecutive samples and average the results over the total collection time. For documenting episodic exposures, use high rates ( 7 to 16 Umin) over shorter sampling times. In relatively dean atmospheres, where targeted fiber concentrations are much less than 0.1 fiber/cc, use larger sample volumes (3000 to 10000 L) to achieve quantifiable loadings_ Take care, however, not to overload the filter with background dust[31. 5. At the end of sampling, replace top cover and small end caps. 6. Ship samples upright with conductive cowl attached in a rigid container with packing material to prevent jostling or damage. NOTE: Do not use untreated polystyrene foam in the shipping container because electrostatic forces may cause fiber loss from sample filter_ SAMPLE PREPARATION: 7. Remove circular sections from any of three quadrants of each sample and blank filter using a cork borer[41. The use of three grid preparations reduces the effect of local variations in dust deposit on the filter. 8. Affix the circular filter sections to a dean glass slide with a gummed page reinforcement. Label the slide with a waterproof marking pen. NOTE: Up to eight filter sections may be attached to the same slide. 9. Place the slide in a petri dish which contains several paper filters soaked with 2 to 3 mL acetone. Cover the dish. Wait 2 to 4 min for the sample filter(s) to fuse and clear. NOTE: The"hot block" clearing technique [51 of Method 7400 or the DMF clearing technique [61 may be used instead of steps 8 and 9. 10_ Transfer the slide to a rotating stage inside the bell jar of a vacuum evaporator. Evaporate a 1- by 5-nm section of a graphite rod onto the cleared fiiter(s). Remove the slide to a dean, dry, covered petri dish [41. Prepare a second petri dish as a Jaffe wick washer with the wicking substrate prepared from filter or lens paper placed on top of a 12-mm thick disk of clean, spongy polyurethane foam [7]. NIOSH Manual of Analytical Methods(NMAM), Fourth Edition,8115/94