Filter cartridge having location-registered view window for end-of-service-life-indicator (ESLI)

A mask body that comprises one or more filter cartridges, wherein the one or more filter cartridges comprise a sorbent filter material that has first and second major surfaces;

• an end-of-service-life-indicator (ESLI);
• a housing into which the ESLI and the sorbent filter material are located, the housing comprising a sidewall through which the ESLI can be seen, and the sorbent filter material being disposed in the housing such that the second major surface of the filter material is disposed downstream to the first major surface;
• a cover that is secured to the housing defining a plane substantially parallel to the first and second major surfaces of the sorbent filter material, the cover having an opaque extension perpendicular to the plane of the cover that masks at least a portion of the housing sidewall;
• and a window that is positioned on the extension at a registration position.

A respirator that comprises:

• (a) a mask body;
• (b) a harness attached to the mask body;
• and
• (c) one or more filter cartridges attachable to the mask body, the filter cartridges comprising a cover, a housing, a filter material, and an end-of-service-life-indicator (ESLI), the filter material and ESLI being disposed in the housing such that the ESLI may be seen through a sidewall of the housing, the cover defining a plane substantially parallel to the filter material and having an extension that extends perpendicular to the plane of the cover and masks at least a portion of the sidewall with a window disposed thereon in a registration position for viewing the ESLI.