| 摘要 |
PURPOSE:To widely secure the effective space for the flowing conditions of a laminar flow of a clean gas in a high-degree clean zone and improve the cleaning degree of a low-degree clean zone by providing a third blow-off port through which a clean gas is downwardly blown off, and disposing a second blow-off port so that the clean gas blow-off flow line is directed toward an oblique downward direction in which the lower part is gradually spaced further from the bordery zone. CONSTITUTION:The flow speed in a bordery zone C of a clean gas blown off perpendicularly downward from a third blow-off port 16 is set by the adjustment of a damper 18 in such a manner that the flow speed of the clean gas therein becomes substantially equal to that of the clean gas at a portion located on the side of the bordery zone C within a high-degree clean zone. Accordingly, it is made possible to widely secure over the whole zone an effective space in which the flowing condition of the laminar flow is stable without disturbing the clean air flowing condition in the high-degree clean zone A by the clean air blow-off through a third blow-off port 16. Further, since the clean air blown off from the second blow-off port 4 assumes a direction obliquely downward toward the central side in the tunnel width direction of a low- degree clean zone B, invasion of adhering dusts and dirts can be effectively prevented even if the operator approaches the high-degree clean zone A. |
