A method of quenching a material by injecting a cryogenic fluid into a cooling stream and simultaneously venting gas from the cooling stream, in order to maintain a desired target pressure in a chamber containing the material. In a examplary application of the method, the quenching is a step in the heat-treatment of a metal and the chamber is part of a vacuum furnace. Also disclosed is a method of supplying a cryogenic fluid to a process in which the amount of cryogenic fluid necessary to perform the process is transferred from a storage vessel to a supply vessel via a supply line, after which the supply line is closed. An elevated pressure is maintained by vaporization of a relatively small amount of the cryogenic fluid that is allowed to build in a pressure vessel that is in fluid communication with the supply vessel.