| 摘要 |
The present invention relates to a composite mask, which comprises a first casing, at lease a first filter medium layer and a second filter medium, in which the first filter medium is set outside the first casing, the first casing is set outside the second filter medium layer, and an accommodation groove is set outside the first casing to accommodate the first filter medium layer. The filtering area of the first filter medium layer is smaller than the second filter medium, the pore diameter of the first filter medium layer is larger than the second filter medium, so the second filter medium layer can filter the gas that can not be filtered by the first filter medium layer. Once the first filter medium layer can not be used to filter the gas, another first filter medium layer can replace it to continue filtering the gas. In addition, the material of the first filter medium layer can be changed according to the circumstance, for example, the material filtering the excessive acid gas is used in the free-dust rooms used to produce the semiconductor, and the material restraining the bacteriums or eliminating the bacteriums is used in the hospital. |
