Abstract: A system, container, and methods are provided for containing and handling a toxic gas. The system preferably includes a first container having toxic gas stored therein and a second container including a base and a lid mounted to the base when in a closed position thereby forming an interstitial space therebetween, which base and lid are sealed against leaks out of the second container by a sealing material that may visibly indicates leaks by visibly changing color in response to contact with any toxic gas that has leaked into the interstitial space, or which container system may include a toxic gas sensor or pressure sensor for detecting presence of leakage gas within the interstitial space. The base has an inner chamber formed therein, and the first container is preferably mounted in the inner chamber so that an interstitial space is formed around at least portions of the first container.