Method and apparatus for sterilizing a gas, and device for conditioning and protecting a zone from a space

A method of conditioning and protecting a particular part of a preselected zone, said part being one in which a manipulation is to be effected, against contaminating agents entering from the outside environment, said method comprising:

• providing a substantially laminar stream of an essentially sterile gas which has an upstream end and a downstream end, said laminar stream forming a gas curtain that defines one boundary side of the preselected zone;
• delivering into said particular part of said zone a substantially continuous flow of an essentially sterile conditioned gas, said flow being adjacent the boundary of said zone remote from said gas curtain and in a direction opposite to that of said laminar gas stream and being at a preselected speed adjusted relative to the speed of the laminar gas stream;
• and deflecting said flow arcuately toward the upstream end of said laminar stream to produce an interaction between said flow and said stream which directs said flow along said stream toward the downstream end and thus controls intrusion of said laminar stream into said zone and generates above said part of said zone a very slow, substantially stable circulation of gas which is continuously renewed at a low speed by said flow of sterile conditioned gas and by an exchange between gas from the flow and gas from the laminar stream.