Measuring Dust Levels for Asbestos Brake Maintenance Workers

The brake maintenance operator wore one hand-held aerosol monitor ("HAM") (personal sample) measuring dust levels in his breathing zone, and the other HAM was set beneath the axle of the vehicle (source sample). The computer stored the data on a disk in a file that was later imported into a spreadsheet.

The computer program recorded a maximum of 2,000 readings at a minimum of four second intervals before it had to be reset. Using a spreadsheet program (Lotus 1-2-3®), a plot of the real-time dust levels was constructed. By comparing the plots with the video, the work practices producing changes in dust levels were identified.

Personal and area air samples for asbestos analysis (NIOSH Method 7400-B) were collected on filters. Personal exposures were taken during the entire brake servicing for each vehicle. Area samples near the axle and fender determined fiber concentrations at the source; general shop area samples determined background fiber levels inside the garage, and out-of-door samples determined the environmental level of asbestos.