Abstract: A method of providing gas to a system which separates from a pressurised supply gas, product gas, includes conditioning the supply gas by both cooling and drying the supply gas.

Abstract: An air cycle air conditioning system for conditioning recirculating air from an enclosure includes an enclosure air recirculation loop, a first expansion turbine to which hot pressurized working air is provided, a heat exchanger to which a proportion of the hot pressurized working air is provided, from upstream of the first expansion turbine, and in which heat is exchanged to the cooler expanded air from the first expansion turbine. The working air from the heat exchanger expanded by the first expansion turbine and the cooled pressurized working air from the heat exchanger are combined prior to feeding the combined flows to a second expansion turbine. The system including a mixing apparatus in which the recirculating enclosure air from the loop and the cooled combined working air flows from the second expansion turbine are mixed prior to being provided to the enclosure.