A method or system of determining integrity of a closed container comprising at least one gas. The determination is based on applying a mechanical force to at least one side of the container and transmitting a light signal across at least a portion of an outside surface of at least one side of the container using an optical sensor. The optical sensor is sensitive to the at least one gas inside the container. Detecting a transmitted light signal and determining, based on the detected light signal, if the at least one gas inside the container has been detected outside of the container.