Masks usage time： Mask use time: It is recommended that the use time not exceed 15 hours. For example, if the commute time is 1 hour and the day returns 2 hours, you can use the mask for about 1 week. If the mask is not damaged, contaminated or clogged, it can be reused: if the mask is damaged, contaminated, clogged or breathing difficulties in use, it is recommended to replace it with a new one. 1:This product is a disposable product and cannot be reused after cleaning. More washing will reduce the protective performance, and can not completely protect the health of the respiratory system. 2：The filtering effect of dust, dust, smoke, PM2.5, pollen and other particulate matter exceeds 95%. Prevent non-oily particles: smoke, industrial dust, grinding dust, paint smell, droplets when talking or coughing, etc. description: The mask is divided into three layers to form a three-dimensional breathing space. It has a hidden nasal plastic bridge to prevent fogging, and a hidden nasal cartilage bridge to prevent gaps and reduce harmful substances by adjusting. Highly elastic earhook, lower pressure. feature: Safety with breathing valve, breathable and hypoallergenic; and high filtration capacity. Elastic earhook, no ear pressure. Provide some protective measures to prevent dust or certain toxic substances. Clean and practical, very suitable for carpentry, house cleaning and general maintenance. They are made of non-woven materials and have good skin tolerance and wearing comfort. No fiberglass. It is a good choice for you or your family. One size is most suitable. package: 30/50/100PCS