Methodology—Brake Servicing Case Study on Asbestos

Video exposure monitoring was conducted to evaluate the brake maintenance operation. Two hand-held aerosol monitors (HAM) and a personal computer (Apple II Plus®) measured and recorded dust levels.

The HAM, which measures respirable total dust levels, is a light scattering device; its response is dependent on the optical characteristics of the dust being measured. Because it does not differentiate between asbestos fibers and other dusts, dust concentrations were reported as relative levels (rather than absolute levels) and were used only to compare similar operations.

At the start of the operation, the computer's clock was synchronized with the timer in the video camera that recorded the entire operation on videotape. Sampling pumps were connected by tubing to each HAM, and each HAM in turn was connected by a 25-ft. electrical lead to the computer.