An irreversible
humidity exposure dose indicator device, including a housing sealed at a first end thereof and adapted at a second end thereof to admit ambient gas ingress into an interior volume containing
chromogenic material. The
chromogenic material in contact with water irreversibly absorbs such water to produce a change whose extent is correlative of cumulative
exposure of the device to
humidity. The device may be configured as an indicator card including an intermediate permeable membrane coated on a first side thereof with a layer of a deliquescent
solid and being in contact on a second side thereof with a layer containing a reactive indicator, with a water-permeable layer adjacent to the layer containing the deliquescent
coating, enclosed within a water-impermeable transparent
enclosure. The device can include an opening to the permeable layer that is shielded by a removable member that is removed to initiate the dosimetric process, and permit
water vapor to diffuse through the opening and liquefy the deliquescent material, so that the liquid permeates through the membrane and a visible indication of the location of the wet front is seen as the water contacts the
chromogenic material. A scale can be printed on the exterior of the
enclosure to permit a viewer to see the progress of the indication, e, g. of a color front.