Some observations on frequency of respirator fit tests.

Quantitative respirator fit tests were repeated with workers who had demonstrated adequate fit initially. As the interval between first and second tests increased, it was expected that the rate of failure (penetration of test aerosol greater than 1%) on the second test also would increase. No significant time relationship was demonstrated, but the results suggest that the opposite of our expectation occurred: failure rates decreased with longer time intervals. If confirmed, the results suggest a simple strategy for repeat fit testing.