04628927 is referenced by 30 patents and cites 11 patents.

A face mask in which an air filter insert is confined in place between mask components with a mask main member being at least partially reversible to facilitate filter insert replacement. A filter element, also of a pliable nature, fits within and conforms to the main member. A modified form of mask includes a main member having a liner portion which, during mask use, folds over and confines the filter element in place and, upon temporary unfolding of the liner portion, facilitates filter removal and replacement. Provision is made for support of a countercurrent exchange medium, such as a metallic sponge, within the mask. A modified mask includes a mesh member and a shell secured to the main mask member in a manner permitting the main member to be turned inside out. A further modified mask is of molded construction having an inwardly folded liner portion.

Title
Reversible face mask with replaceable air filter insert
Application Number
555342
Publication Number
4628927
Application Date
March 7, 1986
Publication Date
December 16, 1986
Inventor
Russell G Ward
2050 S.W. 71st Ave., Portland, 97225
OR, US
Agent
James D Givnan Jr
IPC
A61B 7/00
View Original Source