Respirator Leak Detection by Ultrafine Aerosols: A Predictive Model and Experimental Study

The leak performance of half-mask, maintenance-free respirators was studied theoretically and experimentally. A predictive model for the theoretical protection factor and leakage flow has been developed that uses the equation of particle conservation inside and outside the respirator. An experimental study was conducted using NaCl particles of 10 nm in diameter and a condensation nucleus counter as the particle detector. A respirator fitted with controlled leak holes of 20–3000 μm in diameter was tested at steady flow rates of 10, 32, and 100 L/min. Results showed that the aerosol penetration into a respirator was strongly influenced by the filter efficiency, leak hole size, and flow rate through the respirator. The results are in good agreement with theory, but some discrepancy has been noted at lower flow rates and smaller leak hole sizes. For the dust/mist respirators, the experimental protection factor for ultrafine 0.01-μm NaCl particles ranged from 3145 to as low as 3. For the high efficiency dust/m...