What Pressure Class Means
Building light-class duct on a high-class run; seal/support fails
Yellow / Check First2ndBatch 4
What This Helps With
Building light-class duct on a high-class run; seal/support fails
Apprentice words: pressure class
Trade terms: pressure class, static pressure, in. wg, positive/negative
Check First
Which pressure class the run is, positive or negative, and where it changes
What Not To Do
Assume all supply is the same class
What can go wrong: Mixing classes across a system boundary
Better Foreman Question
What pressure class is this section and where does it step down?
Verify With
Reference type: SMACNA
Source to verify: SMACNA pressure classes; project spec / drawings
Safe wording: Explain the idea; the assigned class comes from the engineer's schedule.