MIL-HDBK-1003/3
b) Ductwork pressure-velocity classification may be
different at different parts of any single duct system.
c) SMACNA HVAC duct construction standards should be
used for pressure-velocity classification.
d) SMACNA classifications are based on maximum static
pressure as follows:
STATIC PRESSURE
Pressure Class
Operating Pressure
1/2" WG
Up to 1/2" WG
1" WG
Over 1/2" WG to 1" WG
2" WG
Over 1" WG to 2" WG
3" WG
Over 2" WG to 3" WG
4" WG
Over 3" WG to 4" WG
6" WG
Over 4" WG to 6" WG
10" WG
Over 6" WG to 10" WG
See Figure 10 for an example of how to delineate duct
pressure class designation.
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