Granted Patent
Utility
US 4,146,887 · App. 05/822,028
Respirator cartridge end-of-service life indicator
Inventor:
Peter C. Magnante
Patented Case
View Patent ↗
Granted: Mar 27, 1979
Filed: Aug 5, 1977
Inventor
Peter C. Magnante
Assignee (at issue)
American Optical Corporation
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.