Evaluation of a continuous instrumental method for determination of isocyanates

The response of a Dunlop/ICI Continuous TDI Monitor was evaluated using the NIOSH modified Marcali spectrophotometric method as the reference analytical procedure. Test atmospheres containing low concentrations of toluene diisocyanate were generated and analyzed in both a dynamic diffusion system and a closed test facility; factory analyses were also made. Agreement of simultaneous measurements in the laboratory and in the field verify that the instrument is a valid alternative to the Marcali method. Results obtained following the NIOSH recommended air sampling procedure indicate that two impingers in series are required to adequately trap airborne toluene diisocyanate.