| 摘要 |
PURPOSE:To enable a user to exactly judge the timing for replacing the replace able electrostatic filter of a dustproof mask formed by using this. CONSTITUTION:The circumference of the sheet-like filter media 12 consisting of the electrostatic filter of the dustproof mask 1 having a replaceable filter part 6 is clamped by the inside cap 10 and outside cap 11 of the filter part 6. The inside cap 10 at the inner side of this circumference is parted by a required distance from the inside surface of the filter media 12. At least part 13 of the parted part is composed of an either transparent or colored transparent blank and a limit sample 15 which is a measure for judgment of the timing for replacing the filter media is inserted into this part. |
