Apparatus and methods for improving the safety and efficiency and decreasing the cost of producing liquid gas, such as liquid oxygen, with a small-scale use liquefaction device, according to various embodiments of the present invention. In one embodiment, liquid oxygen barrier may be added to interface between a cryocooler and a dewar to control rate of liquid oxygen escape upon a tipping of the dewar. A boiloff vessel in fluid communication with the dewar allows expanding gas from a tipped dewar to escape while allowing the liquid to safely settle in the boiloff vessel. A temperature sensing circuit, in proximity with a heat dissipator or cold finger of the cryocooler, is operable to break an electrical power circuit of the cryocooler or cooling fan when a sensed temperature exceeds a predetermined temperature. Oxygen purity of a feed stream of gas may be sensed and/or displayed.