Static field route #19592

What do I do when a 45-degree rectangular transition chokes the duct because only one side was sloped?

Airflow/TAB Impacts From Installation⚠️ CHECK BEFORE YOU FIXField answer expansion

📖 Verified core answer

If only one panel is sloped and the duct depth shrinks, the fitting becomes a restriction. Keep the internal area consistent or get an approved revised fitting detail.

Open in Field Rescue Open category

Field verification checklist

Measure the duct depth through the narrowest point of the fitting.
Compare the restricted area to the planned duct size.
Check whether both top and bottom planes track the offset cleanly.
Look for noise, high velocity, or pressure drop risk.
Confirm revised fitting geometry before fabrication or install.

Ask foreman

The 45 offset at [location] clears the beam but pinches the duct depth through the fitting. I think we need a true parallel-plane offset or revised fitting. Do you want this remade before we continue?

Text to foreman

Route options

A Correct it only if the fix is within your assignment and approved method.

B Hold and document if it affects pressure class, listed assembly, material spec, support load path, fire barrier, equipment, TAB, or another trade.

C Bring the foreman/detailer the location, what you checked, and what decision you need before sealing, testing, cover, or startup.

Do not do this

Do not build an offset that clears the beam by choking the duct throat down smaller than intended.

Why this matters

A choked transition can create pressure drop, noise, poor delivery, and TAB problems downstream.

Final verification

Use this as field training guidance. Final direction still comes from the foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, pressure/material schedule, and AHJ/code requirements.

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