To decrease the incidence of pneumoconiosis, we examined dust protective mask performance and its relation to pulmonary function as well as the effects of worker education on the proper wearing of masks. One hundred and seventy-eight workers from 15 factories subject to dust exposure participated in this study. All participants were interviewed to obtain relevant personal information and underwent both a mask leakage and a pulmonary function test. The mask leakage was expressed as a percentage, with under 10% leakage indicating that the dust protective mask worked efficiently. In addition, 23 workers from 2 factories were educated on how to wear masks properly. The average mask leakage was 24.3%, and 58% of workers wore ineffective masks. Though pulmonary function was almost normal, the percent vital capacity (%VC) tended to be lower depending on the mask leakage. Mask education, which was very easy and took only a short time, dramatically decreased average mask leakage from 32.1% to 10.5% (p0.001). Educating workers to wear masks properly might prevent the worsening of pulmonary function in response to dust exposure. Appropriate mask fitness by education could be useful in preventing the development of pneumoconiosis.