Abstract
A passive dosimeter for monitoring occupational exposure to toluene diisocyanate (TDI) was developed. The device is constructed from a 37-mm aerosol cassette. The collection medium used in the dosimeter is 0.5% sulfuric acid (H2SO4). Membranes of both the permeation and diffusion types were evaluated for use in the dosimeter. Microporous Teflon® diffusion membranes exhibited superior performance in terms of surface effects and residual TDI and were chosen for use. Collected TDI is determined as toluenediamine by either colorimetry using a modification of the Marcali technique or fluorometry using fluorescamine reagent. A significant dependence on wind speed was minimized by use of a second microporous membrane as a wind screen. The mass transfer rate of TDI was found to be approximately 0.0152 µg/ppb·hr and was equivalent for the 2,4 and 2,6 isomers of TDI.