Patent ID: 8067110

Claim:
A protective device that comprises an enclosure including a gas inlet, gas outlet and a thin-film multilayer indicator, wherein: A) the enclosure contains sorbent media that can sorb a vapor of interest flowing from the inlet towards the outlet; B) the thin-film multilayer indicator comprises: i) a porous detection layer whose optical thickness changes in the presence of the vapor, located between ii) a semireflective layer viewable from outside the enclosure and iii) a reflective layer that contains metal particles and that is permeable to the vapor; and C) the reflective layer is in sufficient proximity to the media such that with equilibration at the applied vapor concentration between at least a portion of the media and the vapor, the vapor can pass from the media through the reflective layer and into the detection layer and change the detection layer optical thickness sufficiently to cause a visibly discernible change in the indicator appearance as viewed through the semireflective layer.