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Apprentice Q&A · #169

Under what conditions am I allowed to use flex duct in a commercial kitchen?

4th YearCode & ComplianceRED · Stop / Verify

Almost never. You are explicitly prohibited from using flexible air duct runs inside any commercial kitchen extraction system handling hazardous grease-laden or moisture-laden vapors (Type 1 or Type 2 hood lines). The exhaust air must travel through continuous, heavy-gauge, smooth rigid metal ductwork to prevent grease traps and allow structural fire protection wrap containment.

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Plain-English answer

Almost never. You are explicitly prohibited from using flexible air duct runs inside any commercial kitchen extraction system handling hazardous grease-laden or moisture-laden vapors (Type 1 or Type 2 hood lines). The exhaust air must travel through continuous, heavy-gauge, smooth rigid metal ductwork to prevent grease traps and allow structural fire protection wrap containment.

Field checklist

Ask Foreman

Hey boss, I’m on code & compliance and need verification before I touch this: Under what conditions am I allowed to use flex duct in a commercial kitchen? Do you want me to stop here and check the approved detail, submittal, or inspector/manufacturer requirement first?

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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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Related mistakes & recovery checks

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