FIELD PERFORMANCE-MEASUREMENTS OF HALF-FACEPIECE RESPIRATORS - DEVELOPING PROBABILITY ESTIMATES TO EVALUATE THE ADEQUACY OF AN APF OF 10

To evaluate the protection provided by negative-pressure, half-facepie ce respirators, ambient and in-facepiece samples were collected on wor kers in foundry, aircraft-painting, and steel-manufacturing operations . Protection was assessed by workplace protection factors (WPF). The a ppropriateness of the assigned protection factor (APF) for half-facepi ece respirators was evaluated with a new approach using the WPF data f rom these and other studies previously published. The new approach uti lizes binomial statistics based on the number of successes (no overexp osure) and failures (overexposure) and is illustrated with a graphical representation of WPF data. With this consideration of the data, the probability of overexposure occurring during a wearing period for work ers wearing the half-facepiece respirators represented by the studies referenced here was 0.5%, with a 95% confidence interval of 0.01 to 2. 7%. If 50% in-facepiece sampling errors are considered, the probabilit y of overexposure was 2.9%, with a 95% confidence interval of 1.1 to 6 .3%. The authors believe the current APF of 10 for half-facepiece resp irators is appropriate.