Measurement of 2,4-toluene diisocyanate concentrations by different samplers.

The standard sampling methods for toluene diisocyanate (TDI) only collect total TDI without separating the aerosol and gas phases. There are few other samplers, such as the dual filter, triple filter and annular denuder systems (ADS), which are able to sample the aerosol and gas phases simultaneously. This field study was conducted at two workplaces to access the total 2,4-TDI and the gaseous and aerosol TDI concentrations by different samplers simultaneously. In addition to the standard sampling time of 15 min, sampling was done for 30 and 60 min to study the effect of sampling time on the measured 2,4-TDI concentrations. Test results at two workplaces show that gas-phase 2,4-TDI is the predominant species and the aerosol phase concentration is very small. The measurements using various samplers show that the sampling time influences the sampled TDI concentration considerably which may be due to reaction of TDI with water vapor and polyo in the sampling process. It is evident that as sampling time increases the TDI concentration decreases. Laboratory test was also conducted using pure gas-phase 2,4-TDI to confirm the sampling time effect on the measured concentrations found in the field study.