The mask expired unopened, is no protection effect. First of all, from the design of the mask, it mainly includes three layers of materials, the outermost layer is waterproof layer, the inner layer is moisture-proof and anti-absorbent layer, and the middle layer is meltblown cloth. The use effect of the mask will be worse and worse with the extension of time, and the protection function will be greatly reduced. If it appears that the mask is unopened but has expired, it is best not to use it. Although the mask may be sterile, the protective function is not as good as it used to be. Try to get a new mask, a disposable medical surgical mask or an N95 mask, which can be very good for protection. It is not recommended to use expired masks, even if they are not unsealed, the protective function is not as effective as before.