Are major holes in the floor(s) of the building where there is no floor. May include stairs, shafts, flues, major pipe shafts, vertical ducts, and the like, which penetrate more than one floor. Does not include stairs, dumb-waiters, etc., exclusively serving a single tenant occupying offices on more than one floor. These penetration may or may not include their enclosing walls depending on the measurement standard used or the type of penetration.
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