The structure of dust mask shall conform to the requirements shown in the following each item.
1. It must be not easy to break.
2. It must be easy to wear, and not to give a pressed feeling or pain when being worn.
3. The dead space must not be too large.
4. It must not remarkably narrow the visual field of the wearer.
5. The respirator having full-face type facepiece should not be dimmed at eyepiece(s) by exhalation.
6. Those dust mask having replaceable filter cartridge(s), inhalation valve(s), exhalation valve(s) and head harness should be so designed that those replaceable parts are easily replaced. And, the air tightness between face and facepiece can be easily checked anytime by wearers themselves.
7. On the disposable dust mask, the filtering facepiece must keep the shape within the service duration without deform.
8. On the disposable dust mask, inward leakage and wet breathing resistance must not be remarkably high.
9. In the disposal dust mask, if facepiece is made of the filtering material, it must be formed so that the filtering facepiece is fitted to face.
The individual part of dust mask shall conform to the requirements described in the right column of the following Table, according to the part described in the left column of the same Table.