Self appearing warning sign device and method of manufacture

摘要: A self-appearing warning sign device and method for the manufacture of a including relatively thin gas impermeable support member upon which coating is superimposed having composition containing one or more chromographic reagents will cause visible color change in presence specified polluting gas. The has raised thickness between about 5-500 microns. defined shape formed depositing given identifying by masking area to form said shape. also includes hydrophobic layer end covers an arrangement forming tight sealed enclosure except opening each cover on opposite ends device.