Appendix B: Traversing a Duct to Determine Average Air Velocity or Volume
65
0.061 H
0.235 H
0.437 H
0.563 H
0.765 H
0.939 H
H
0.074 V
0.288 V
0.500 V
0.712 V
0.926 V
V
Figure 32: Location of Measuring Points for Traversing a
Rectangular Duct using Log-Tchebycheff Method
For this duct, a 30-36” horizontal dimension requires 6 points (or 6 traverse lines). For this duct, a vertical
dimension less than 30” requires 5 points (or 5 traverse lines).
# of Points or
Traverse Lines
per Side
Position Relative to Inner Wall
5
0.074, 0.288, 0.500, 0.712, 0.926
6
0.061, 0.235, 0.437, 0.563, 0.765, 0.939
7
0.053, 0.203, 0.366, 0.500, 0.634, 0.797, 0.947
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