Asbestos removal evaluation lab report, schools

NYC 9/11 Public Portal Document wa a we od we oes me ow he 2 —_ «pant . C8, SRO EES 1 emmeetnted S ’ . canara * Ti . | ; | 146 SETTLED ASBESTOS DUST SAMPLING AND ANALYSIS "ings had been removed from the cafeteria and the area had been vacuumed with a conventional dry vacuum cleaner twice before the samples were collected. Previous use and traffic pattems were not taken into account in collecting the sampics. The samples were collected in a random manner and some sampics may have been from areas where an appliance such as a soft drink machine may have stood previously. The data which include some interlaboratory comparisons are presented in Table 1. Although, there appears to be one outlier in the data set, the relative standard deviation was Calculated using ail eight data points for cach method. The S, for the microvacuum technique was 77% and for the bulk-carpet sonication proce- dure was $1% for Lab A and 47% for Lab B. The mean recovery of the enicrowacuuming technique compared to the bulk-carpet sonication procedure was 1%. ‘The answer to the question about which method is best for assessing the asbestos tevel in carpeting depends on the specific question being asked. In the 1988 EPA carpet study the authors concluded that sonication of bulk- carpet samples provided a more precise and accurate estimate of asbestos concentrations in carpet than the microvacuuming sampling technique. Their conclusion was based in part on data which showed that the micro- vacuuming technique was shown to secover significantly less asbestos from the carpet than the ultrasonic extraction The fact that one technique is more efficient in recovering fibers than the other may be important for some studies investigating the cleaning of the total carpet. However, there is reason to believe that carpets can act as a trap for asbestos fibers and that activities short of carpet removal may not disturb asbestos fibers which have worked theic way deep into the carpet For those fibers which can be readily reentrained into the air from the carpet surface during cleaning activities, the microvacuuming procedure may be more eppropriate. This is reasonable considering that the microvacuum- ing procedure collects fibers from the top layer of the carpet and the bulk- carpet sonication procedure shakes oul more fibers which may be embedded deep in the carpet pile. The data show that the sonication of bulk-carpet samples is a more precise procedure than the microvacuuming procedure. However, the microvacauming procedure has an advantage of being non- destructive. While some building owners may be willing to have a picce of carpeting cut from their building if the carpet is to be removed, it is less * at dete NYC-WTC_000144623