In a semiconductor-fabrication equipment of a minienvironment system, ambient air is prevented from entering a gap between an opening of the semiconductor-fabrication equipment and a wafer gateway of a hermetic container to prevent dust entrained in the ambient air from adhering to wafers in the hermetic container. Clean air is injected from a clean-air injection device (1), which is connected to an air-supply device (2) through an air-supply tube (3), and which is provided with filter means (6a) in the from of rectangular frame formed with cylindrically-shaped filters connected to each other, to form an air curtain at the gap (96) between the gateway (74) of the hermetic container (71) through which wafers (73) are taken out of or put in the hermetic container (71) and the opening (98) of a loading part (78) attached to a front panel (77) of the semiconductor-fabrication equipment (76), thereby shutting off the ambient air that would otherwise enter the hermetic container (71) through the gap (96) between the gateway (74) of the hermetic container (71) and the opening (98) of the loading part (78) attached to the semiconductor-fabrication equipment (76) when a lid (75) of the hermetic container (71) is opened into the semiconductor-fabrication equipment (76).