A diffusive sampler for personal monitoring of toluene diisocyanate (TDI) exposure; Part I: Design of the dosimeter

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 micrograms/ppb.hr and was equivalent for the 2,4 and 2,6 isomers of TDI.