In previous experiments, four types of face masks including fabric/cloth, surgical and for-air-mask, particulate respirator masks were evaluated for PMs removal efficiency (RE). The highest RE is from dedicated particulate respirators with the rating equivalent to N95. With particles in the ambient air as the reagents, the new masks filered out about 90% PM2.5. The price of those brandname masks is from 35 to 50kVND (US$1=23kVND) is not affordable to change the the mask weekly for low to medium income workers. The interest of reused the masks motivated the author to test the RE of used masks. The used or with washed masks showed a acceptable RE from 75% to 90%, a slightly lower than the new ones. The outcome suggests that washing and reusing the used masks are possible. The number of washes are limited to one-to-two times which also intended by the authors because of these masks are not made for reused. The recommendation for these masks are for days to weeks before disposal.