| 摘要 |
<p>An improved indicator (10) includes a base member (12); an indicating material layer (14); an adhesive layer (16); and a layered covering material (18). The indicating material layer (14) provides a visual indication when exposed to a selected component of an ambient fluid and is applied to one side of the impermeable base member (12) in a selected pattern. The adhesive layer (16) is made of an impermeable material and applied in a selected pattern over the indicating material layer (14) leaving one selected portion of the indicating material (14) exposed to the ambient fluid. An inner layer (22) of the co-layered cover member (18) is permeable to the ambient fluid. The useful life indicator (10) remains in a selected state of dormancy until an outer layer (20) of the co-layered cover member (18) is removed. The indicator (10) may include a self-contained norm of visual indication.</p> |
