Colorimetric indicator for the indication of the exhaustion of gas filters
US4684380A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 13, 1985 |
| Grant date | Aug 4, 1987 |
| Priority date | — |
| Expiry date | Dec 13, 2005 |
Classification
- Technology area (CPC A)Human Necessities
- CPC primaryA62B18/088
- WIPO fieldOther consumer goods
- WIPO sectorOther fields
Abstract
Gas filters protect the user of respirator equipment against the inspiration of harmful gases. The protection decreases with the use of the filter. To alert the user in time to the imminent exhaustion of the filter material, the respirator is equipped with an indicator that makes the remaining time of use visible through optical characteristics such as color change. The indicator provides for the inclusion of an indicator granulate loosely filled between two discs and permeable to the respiration gas, which changes its color as it detects a gas to be filtered out. The indicator is located in a container open to the gas flow which is covered by an inlet screen and it extends to a given immersion depth into the filter material. The immersion depth guarantees that the respiration gas flows uniformly through the indicator with each inspiration.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.