Control of the atmosphere in an enclosure

摘要

A method of controlling an atmosphere in an enclosure (12) to which gas (40) is being supplied comprises the steps of monitoring (53) atmospheric pressure within the enclosure and the rate of gas flow to (52) or from the enclosure, comparing these parameters (62) with adjustable set points to obtain error values and adjusting inflow (50) and exhaust (51) valves for the enclosure in dependence upon the error values. A preferred method includes the intermediate steps of deriving from the error values, target positions for the valves. Also disclosed is an installation incorporating a control system for carrying out the method.