Carbon dioxide indicator device

Claim 1

A combination rapid response device for the detection of carbon dioxide in a gas mixture which comprises an enclosure defined by walls and having a transparent window in one of said walls, an inlet, an outlet and atmospheric sealing means, said enclosure having mounted therein an indicator component positioned and arranged so as to be viewed through said transparent window, said component comprising a carrier having fixedly attached thereto an indicating element formed from (1) an aqueous solution of a colorless compound which provides an alkaline solution; (2) a hygroscopic, high boiling transparent, colorless, water-miscible liquid; and (3) a chromogenic pH-sensitive indicator which changes color relative to a change in pH of the solution and which has a pK which is lower by 1.0-1.5 pH units than the pH of the solution, wherein the nature and concentration of the colorless compound in (1) is correlated to the nature and concentration of the indicator (3) so that no color change occurs for at least 15 minutes when the indicating element is exposed to an atmosphere having a concentration of 0.03% carbon dioxide, but a color change is produced within 5 to 20 seconds when said indicating element is exposed to an atmosphere containing at least 2% carbon dioxide, said sealing means enclosing said device and being constructed so as to be opened immediately prior to use of the device.