Abstract: A cleanroom has an inner chamber inside of which are disposed prescribed semiconductor device production equipment, an interface box, and an interface box opener and the like, and an outer chamber which surrounds the inner chamber, and which forms an air circulation path between itself and the inner chamber, wherein air inside the inner chamber circulates in the air circulation path via a fan filter unit provided in the inner chamber, a clean second air flow, independent from the first air flow circulating in the inner chamber and air circulation path, being directly supplied to a region near the interface box opener from the outside of the cleanroom.

Abstract: A method for measuring a direction of a laminar air flow uses a particle stream tracing an air flow and having a grain size substantially uniform along the particle stream. The direction of the particle stream is detected by a first and a second rectangular laser beams crossing each other in the vicinity of the particle stream at right angles and rotatable around an axis passing through the cross point of the laser beams. The second laser beam is further rotatable around the axis thereof. When the particle stream crosses the laser beams along the longer sides of the rectangular radiant area of the laser beam, the amount of a scattered light generated from the laser beam is large. Hence, the direction of the particle stream is detected by the rotational angle of the second laser beam. The direction of an air flow can be measured with a good accuracy because the measurement does not disturb the original air flow.