Respirator cartridge end-of-service life indicator

In a respirator cartridge having a covered shell with oppositely disposed upstream and downstream perforated sides for passage of air therethrough, the combination of an adsorbent for an organic vapor/gas supported between said perforated sides and an end-of-service life indicating system within said adsorbent adjacent said upstream side of said shell including an indicator characterized to undergo a change of color concomitant with exposure to concentrations of organic vapors and gases which are below a threshold limit known to be safe to inhale, said indicating system including the improvement of molecular sieve material between said indicator and said perforated upstream side of said covered shell with said sieve material adjoining said indicator for adsorbing molecules of matter within a range of molecular size including those of H.sub.2 O while permitting passage of larger molecules of organic vapors and gases for rendering said larger molecules passed through adaptable to intimate contact with said indicator and immediate reaction therewith.