Code references

Dryer Vent Code References

M1502.2 Concerning Duct Terminations
Exhaust ducts shall terminate on the outside of the building or shall be in accordance with the dryer manufacturer’s installation instructions. Exhaust duct terminations shall not be less than 3 feet in any direction from openings into buildings. Furthermore, exhaust duct terminations shall be equipped with a backdraft damper. Screens shall not be installed at the duct termination.
M1502.3 Concerning Duct Sizes

The diameter of the exhaust duct shall be as required by the clothes dryer’s listing and installation instructions.

M1502.4 Concerning Transition Ducts or Flex Hoses

Transition ducts shall not be concealed within construction. Flexible transition ducts used to connect the dryer to the exhaust duct system shall be limited to single lengths not to exceed 8 feet and shall be listed and labeled in accordance with UL2158A.

M1502.5 Concerning Duct Construction

Exhaust ducts shall be constructed of minimum .016 inches (0.4mm) rigid metal ducts, having smooth interior surfaces, with joints running in the direction of air flow. Exhaust ducts shall not be connected with sheet metal screws for fastening.

M1502.6 Concerning Duct Lengths
The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet from the dryer location to the wall or roof termination. Additionally, the maximum length of the duct shall be reduced 2.5 feet for each 45 degree bend, and 5 feet for each 90 degree bend. Finally, the maximum length of the exhaust duct does not include the transition duct.

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