Evaluation of air-purifying respirators for protection against toluene diisocyanate vapors.

Abstract

Two brands of air-purifying organic vapor cartridges (Willson and Survivair) and a disposable respirator (3M) were evaluated for protection against toluene diisocyanate (TDI) vapors. The respirators/cartridges were tested by generating dynamic atmospheres of TDI at concentrations of 0.2 and 1.5 ppm or greater, which are substantially above the currently accepted exposure limits. The TDI atmospheres were generated by controlled and continuous evaporation and dilution techniques. The relative humidity of the final TDI atmosphere was maintained at 50%. For the testing of Survivair and Willson respirators, one cartridge was mounted on a stainless steel plate and placed inside an exposure chamber through which air was drawn unidirectionally at 32 L/min. Periodically, the air before and after the cartridge was monitored for TDI. In the case of the disposable, valveless 3M respirator, a breathing pump was used to simulate the breathing through the respirator. The TDI atmosphere was respired through the respirator at 28.8 L/min (24 cycles/min at 1.2 L/cycle). As before, the concentration of TDI was measured periodically before and after the respirator. There was no significant breakthrough (less than 0.5%) of TDI in any of the respirators tested for 40 hr at 0.2 ppm and for 20 hr at 1.5 ppm or higher concentration of TDI. The detection limits of the post-respirator TDI measurements ranged from 0.4 to 0.02% of the pre-respirator concentration. It is important to note that, at the present time, because the odor threshold for TDI is higher than the ceiling exposure limit (poor warning property), NIOSH and most of the respirator manufacturers do not recommend the use of air-purifying respirators in isocyanate containing environments.