| 摘要 |
This invention relates to a fume hood controlling method and apparatus which reduces the amount of replacement air required to operate a fume hood (10) by permitting the fume hood to operate at a relatively low face velocity in the absence of a containment affecting condition, but which is capable of detecting the occurrence of a containment affecting condition, such as the presence or movement (34) of a user within a selected area of the face of the fume hood, and of increasing face velocity to a selected level in response to such detection. When the detected condition no longer exists, the control automatically returns the fume hood to the lower face velocity, preferably with a time delay. Maximum replacement air volume and minimum replacement air volume may also be controlled in response to such detection.
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