TinnerFlow™2nd YearFlex Duct & GrillesRED · Stop / Verify
The maximum code length for flexible air duct is 5 feet for traditional commercial systems, though some jurisdictions or project specs allow up to 6 feet. Flex duct should only be used for the final terminal connection to the diffuser-never as a substitute for hard trunk pipe.
The maximum code length for flexible air duct is 5 feet for traditional commercial systems, though some jurisdictions or project specs allow up to 6 feet. Flex duct should only be used for the final terminal connection to the diffuser-never as a substitute for hard trunk pipe.
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.