Abstract: A solution for detecting concentrations of CO.sub.2 is sealed within a pouch located on or in a food container and visually observable from outside the container. A microporous material places the indicator in gaseous communication with the food contents of the container, while maintaining isolation from the food liquids and solids. As a result, the indicator is responsive only to CO.sub.2 gas evolved within the container, and is unaffected by the particular pH of the food within the container. The CO.sub.2 detector provides a visual change when CO.sub.2 gas is detected, thus indicating probable deterioration of the food contents of the container.