Patent ID: 6987554

Claim:
An apparatus comprising: a chamber; a cooler to cool an inert gas to be supplied to said chamber; a circulating path in which the inert gas flows through said chamber and said cooler; a first path, connected to said circulating path at a first position downstream of an outlet port of said cooler and upstream of said chamber, to introduce air to said circulating path; a second path, connected to said circulating path at a second position downstream of said chamber and upstream of an inlet port of said cooler, to exhaust gas in said chamber; a first shut-off valve, arranged in said circulating path upstream of the first position and downstream of the outlet port of said cooler, to close before the introduction of the air; and a second shut-off valve, arranged in said circulating path downstream of the second position and upstream of the inlet port of said cooler, to close, to prevent the air from flowing to said cooler.