Suggest replace the fliters every week of uses for the best effect. ★Multi-layer protection allows you to avoid contact with bacteria, dust, haze, car exhaust, and pollen. ★Exhalation Valve allows air to flow out freely,high Quality fabric make your family or friends feel more comfortable. ★Scope: dust masks, self-use masks, beauty salons, pet shop masks, factory masks, food processing masks, environmental cleaning masks and other protective dust can be placed.