Document X8rBo2vpbpRzv41Kby3z1XN6B

Clayton tmironmental Consultants, Inc. 4 2- - locations equidistant from the vacuum cleaner exhaust port. An additional area sample,' located in the. north, east corner of the room, was taken immediately after the vacuum cleaner iss turned off. The room was then venti lated for approximately two hours to minimize the possi bility of interference with subsequent tests. To reduce the possibility that fibrous dust, which might normally he present in the indoor air, or fibers generated by a previous test might interfere with the analyses of the test samples, "control" samples were taken immediately prior to each of the tests before any hand\ing of the asbestos-containing dust. Since it would be difficult, if not impossible, to simu late with a commercial asbestos product actual "brake dust," with respect to particle and fiber size distribu tions end thus to simulate the efficiency with which the fibers were removed by the- vacuum cleaner filtration sys tem, it was desirable to use for the evaluation actual asbcstos-containi r.p. dust generated in a manner similar to that associated with automobile maintenance procedures, c.g., grinding of brake shoes. A bulk sample of dust pro duced by grinding of brak-. shoes was obtained from a local automotive a:;lc plant. This dust had been collected by fabric filters incorporated in the plant's local exhaust ventilation systems. The physical appearance of the dust was that of a very fine, dry, Ri'iyish-brovn powder simi lar in consistency to talcum or face powder. No other dust was mixed with the brake dust during or after en trainment by the exhaust-fi11rat i on systems. The dust was analyzed in the Clayton laboratory for percent fiber and fiber length distribution by phase contrast micro scopy at 400X magnification. The results indicated that the dust was composed of approximately 19.4 percent fiber (i.c. , fiber to particle ratio), and that fiber lengths ranged from approximately four micrometers to greater than fifty micrometers. Apprcximate1y four percent of the fibers were less than si:: micrometers in length, about forty-two percent measured betwter six end twelve micrometers, and the remaining fifty-iour` percent meas ured greater than twelve micrometers in length. sampling and analytical methods both general jrve and breathing zone samples were col lected by droving air at a nominal flowrate of two liters p:r minute through Is 7. mm- diameter cellulose eater mem brane filter.- : Mi ) 1 i oorv, Type AA, nominal pore site ).E % micrometer-} m. .tunica i v a cvrec-pioct c ...> c 11 u v,jt.t t...cover removed,- uaing portable battery-operated pumps (Mine v 8005 1583 PRODUCED BY FORD