Abstract: The carbon dioxide sensor includes a CO.sub.2 sensing matrix formed from a hydrophilic, gas permeable, cross-linked polyurethane. The polyurethane matrix is formed from a polyurethane pre-polymer mixture which cross links when mixed with an aqueous carbon dioxide buffer solution. The dye-buffer solution is physically entrapped as a homogeneous dispersion in the polymer matrix. The matrix is applied to the exposed glass core of an optical fiber, which may first be coated with a primer to allow the polyurethane matrix to bond firmly to the tip of the optical fiber. The hydrophilic polymeric matrix is preferably coated with a hydrophobic material to help avoid leaching of the dye from the matrix, and to prevent diffusion of hydronium ions into the sensing matrix. The hydrophobic polymer overcoat may thereafter be cured by heat treatment. The hydrophobic coating may also contain a light reflective material such as TiO.sub.2.

Abstract: The method of stabilizing a carbon dioxide sensor involves formulation of a bicarbonate buffer solution in the sensor with a bicarbonate ion concentration of from about 100 mM to about 200 mM bicarbonate. The method also involves treatment of the sensor to reduce the instability that may occur in carbon dioxide sensors when such sensors are exposed to either very low or very high carbon dioxide levels for extended periods of time. The sensor is treated by exposing the sensor to an aqueous solution containing at least 2 weight percent carbon dioxide, for from several days to several months. The solution may be prepared in advance, or may be dynamically infused with carbon dioxide to provide the desired carbon dioxide content.

Abstract: The method of stabilizing a carbon dioxide sensor involves treatment of the sensor to reduce the instability that may occur in carbon dioxide sensors when such sensors are exposed to either very low or very high carbon dioxide levels for extended periods of time. This is accomplished by storing the sensor in an aqueous solution containing at least 2 weight percent carbon dioxide, for from several days to several months. The solution may be prepared in advance, or may be dynamically infused with carbon dioxide to provide the desired carbon dioxide content.