PARTICULATES NOT OTHERWISE REGULATED, RESPIRABLE: METHOD 0600, Issue 3, dated 15 January 1998 - Page 4 of 6
Bias can also be caused in a cyclone by the pulsation of the personal sampling pump. Bartley, et al. [12] showed that cyclone samples with pulsating flow can have negative bias as large as −0.22 relative to samples with steady flow. The magnitude of the bias depends on the amplitude of the pulsation at the cyclone aperture and the dust size distribution. For pumps with instantaneous flow rates within 20% of the mean, the pulsation bias magnitude is less than 0.02 for most dust size distributions encountered in the workplace. Electric charges on the dust and the cyclone will also cause bias. Briant and Moss [13] have found electrostatic biases as large as −50%, and show that cyclones made with graphite-filled nylon eliminate the problem. Use of conductive samplers and filter cassettes (Omega Specialty Instrument Co., 4 Kidder Road, Chelmsford, MA 01824) is recommended. 2. Precision: The figure 0.068 mg quoted above for the precision is based on a study [3] of weighing procedures employed in the past by the Mine Safety and Health Administration (MSHA) in which filters are pre-weighed by the filter manufacturer and post-weighed by MSHA using balances readable to 0.010 mg. MSHA [14] has recently completed a study using a 0.001 mg balance for the post-weighing, indicating imprecision equal to 0.006 mg. Imprecision equal to 0.010 mg was used for estimating the LOD and is based on specific suggestions [8] regarding filter weighing using a single 0.001 mg balance. This value is consistent with another study [15] of repeat filter weighings, although the actual attainable precision may depend strongly on the specific environment to which the filters are exposed between the two weighings. REFERENCES: [1] Bartley DL, Chen CC, Song R, Fischbach TJ [1994]. Respirable aerosol sampler performance testing. Am Ind Hyg Assoc J, 55(11): 1036–1046. [2] Bowman JD, Bartley DL, Breuer GM, Shulman SA [1985]. The precision of coal mine dust sampling. Cincinnati, OH: National Institute for Occupational Safety and Health, DHEW (NIOSH) Pub. No. 85-220721. [3] Parobeck P, Tomb TF, Ku H, Cameron J [1981]. Measurement assurance program for the weighings of respirable coal mine dust samples. J Qual Tech 13:157. [4] ACGIH [1996]. 1996 Threshold limit values (TLVs™) for chemical substances and physical agents and biological exposure indices (BEIs™). Cincinnati, OH: American Conference of Governmental Industrial Hygienists. [5] American Conference of Governmental Industrial Hygienists [1991]. Notice of intended change— appendix D—particle size-selective sampling criteria for airborne particulate matter. Appl Occup Env Hyg 6(9): 817–818. [6] NIOSH [1977]. NIOSH Manual of sampling data sheets. Cincinnati, OH: National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 77-159. [7] Higgins RI, Dewell P [1967]. A gravimetric size selecting personal dust sampler. In: Davies CN, Ed. Inhaled particles and vapors II. Oxford: Pergammon Press, pp. 575–586. [8] Bowman JD, Bartley DL, Breuer GM, Doemeny LJ, Murdock DJ [1984]. Accuracy criteria recommended for the certification of gravimetric coal mine dust personal samplers. NTIS Pub. No. PB 85-222446 (1984). [9] Breslin, JA, Page SJ, Jankowski RA [1983]. Precision of personal sampling of respirable dust in coal mines. U.S. Bureau of Mines Report of Investigations #8740. [10] Bartley DL, Breuer GM [1982]. Analysis and optimization of the performance of the 10-mm cyclone. Am Ind Hyg Assoc J 43: 520–528. [11] Caplan KJ, Doemeny LJ, Sorenson S [1973]. Evaluation of coal mine dust personal sampler performance, Final Report. NIOSH Contract No. PH CPE-r-70-0036.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
