The masks are made of three layers of non-woven materials, and the front and back sides need to be distinguished, otherwise they cannot be worn correctly, and the protective effect that the masks shoul...

Why should we correctly distinguish the front and back of the mask? Many people may think that the positive and negative sides are the same, as long as Dai Yanshi is done. In fact, this is not the case...

The epidemic is quite serious recently. Many friends have put on masks, but the masks are not necessarily correct. Do you know the correct way to wear masks? Taking the disposable mask as an example, t...

The front and back of the white flat mask can be distinguished by metal strips, creases, thread ends, colors and fabrics. 1. Metal strip distinction Differentiated by metal strips, usually the color of...