Venting

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I loved the title “Blowing budget” (CleanRooms, May 2000, p. 15) and the article was excellent in the area of cost tradeoffs between new and old facilities.

However, air simply never gets to the corners illustrated in the maps on page 16. Instead it will follow the path of least resistance to the diagonal corner; more of an arch in this case than a right angle. In order to get it into those corners, one would have to install pulling blowers at those locations and subsequently duct that air elsewhere or allow it to re-enter the plenum at some other less-critical point.

This example points out the serious flaws in computer analysis and/or in its users.

• If you set up the configuration as a PUSHER there is nothing other than “user knowledge” or “the inquiring mind” that would tell you that PULLING is more efficient.

• If the fundamental parameters are set up wrong the user has to be experienced enough to spot or detect errors or flaws in the results.

Charlie Middleton
Air flow consultant
Sudbury, MA

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