Abstract: A vent tube having a first branch and a second branch for use in a cryogenic container through which the interior of the container is communicated to the atmosphere. The cryogenic container is adapted to receive a fixed volume of cryogenic fluid at a uniform temperature and density. In a filling operation, the first branch of the vent tube contacts the cryogenic fluid and carries a portion of the fluid to the atmosphere to inform an operator that the capacity of the container has been reached. After the container is filled, the temperature in the stored cryogenic fluid rises. As the temperature changes, distinct stratified layers of fluid of different densities and temperatures can be measured in the container. The change in temperature causes the cryogenic fluid to expand and submerge the adjacent first branch of the vent tube.

Abstract: A method and system for supplying a person with breathable fluid in an irrespirable atmosphere. A package which is attached to a person holds a container having a valve which is activated upon removal of a protective cover. The valve allows a breathable fluid to flow at a variable rate to a supply conduit. The supply conduit is connected to a reservoir. An inhalation check valve connects the supply conduit to the person. Upon inhalation, the check valve will open and allow breathable fluid to flow from the supply conduit. Upon exhalation, the inhalation check valve closes and an exhalation check valve opens to permit the breathed air to flow through a filter where carbon dioxide is removed before returning to be mixed with breathable fluid in the supply conduit.