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Apprentice answer

What is the maximum allowable leakage rate for Class A duct sealing

4th YearSealing, Leakage & MasticStop / Verify

Under standard energy conservation codes and SMACNA leak test manuals, a high-pressure commercial duct system specified with a Class A Seal rating must restrict total air volume leakage to under 5% of the total system design CFM capacity when subjected to a full-pressure test verification run.

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Plain-English answer

Under standard energy conservation codes and SMACNA leak test manuals, a high-pressure commercial duct system specified with a Class A Seal rating must restrict total air volume leakage to under 5% of the total system design CFM capacity when subjected to a full-pressure test verification run.

Field checklist

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Hey boss, I’m on code & compliance and need verification before I touch this: What is the maximum allowable leakage rate for Class A duct sealing? Do you want me to stop here and check the approved detail, submittal, or inspector/manufacturer requirement first?

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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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