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Apprentice answer

Do I need to seal the longitudinal seams, or just the transverse joints

1st YearDuct Assembly, Seams & JointsCheck first

Class A Seal Specification: Requires sealing all transverse joints, longitudinal seams (like Pittsburghs), and any fastener penetrations. * Class B: Requires sealing joints and seams only. Always look at the project specs-assume Class A for commercial systems unless told otherwise.

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Plain-English answer

Class A Seal Specification: Requires sealing all transverse joints, longitudinal seams (like Pittsburghs), and any fastener penetrations. * Class B: Requires sealing joints and seams only. Always look at the project specs-assume Class A for commercial systems unless told otherwise.

Field checklist

Ask Foreman

Hey boss, I’m checking sealing & insulation: Do I need to seal the longitudinal seams, or just the transverse joints? I found the likely issue and want to verify the next step before I lock it in. Do you want me to adjust it now or check the drawing/detail first?

Verify before acting

Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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