Abstract: A method and apparatus for providing a clean respirable atmosphere in a clean room. A liquefied breathable gas is supplied from a source thereof and filtered. The filtered liquid is vaporised and the gas produced by the vaporisation is filtered. Thereafter the filtered gas is introduced into the clean room.

Abstract: In the manufacture of moulds or mould cores, refractory sand, a resin binder and a catalyst are passed into a mixer to form a freeflowing mixture from which the moulds or mould cores are made. As the sand is fed into the mixer it is cooled by contact with an atmospheric gas in liquid or solid state or the cold vapour of such a gas so as to keep the temperature of the sand as it enters the mixer below that at which the resin cures. To enable the sand to be delivered below a chosen temperature from a quarry to a foundry where the sand is used, the sand after quarrying and drying is fluidized by air, an atmospheric gas in liquid or solid state being introduced into the fluidizing air so as to lower its temperature.