Most building code now requires a permanent label that delineates the calculated length of the dryer’s exhaust system. This equivalent length covers the exhaust system from the interior wall to the exterior of the structure.

Equivalent Length?
Each sectioned elbow in the system negatively affects the overall length with the only exception being long-turn elbows (i.e: the Dryer-Ell). 45 and 90 degree elbows effectively add 2.5 feet and 5 feet respectively. With the equivalent length identified, the right appliances can be selected, and the appliances that are unable to vent efficiently through the equivalent length can be avoided. In this manner, excessive lint buildup can be avoided and the fire risk can be lessened.

Both duct runs below have an equivalent length of twenty five feet based on the type of elbow employed.

Both duct runs below have an equivalent length of twenty five feet based on the type of elbow employed.

Equivalent Length?
Each sectioned elbow in the system negatively affects the overall length with the only exception being long-turn elbows (i.e: the Dryer-Ell). 45 and 90 degree elbows effectively add 2.5 feet and 5 feet respectively. With the equivalent length identified, the right appliances can be selected, and the appliances that are unable to vent efficiently through the equivalent length can be avoided. In this manner, excessive lint buildup can be avoided and the fire risk can be lessened.

Code Required — Equivalent Length Notification

Now, homeowners can select appliances that meet length requirements set on the label with a permanent marker. And as their builder, can take full advantage of manufacturer run lengths without problems down the road.

Made to last, the 3" X 4" PLAC34 is thick velvet-textured 3M Scotchcal™ 3650-10 substrate with pressure sensitive Hi Tack adhesive that permanently sticks to a wide variety of surfaces including low energy surfaces such as plastics and powder coated paints.

ICC Code Sections IMC 504.8.5 and IRC 1502.4.6:

"Length identification. Where the exhaust duct equivalent length exceeds 35 feet (10 668 mm), the equivalent length of the exhaust duct shall be identified on a permanent label or tag. The label or tag shall be located within 6 feet (1829 mm) of the exhaust duct connection."

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Download the code requirements: (PDF)

 2015 International Mechanical Code

 2015 International Residential Code

Part Number PLAC34

2009 International Mechanical and International Residential Code now require a permanent label showing a duct run's equivalent length.