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Clogged dryer vents are a safety hazard for homeowners’. To reduce the chances of a clogged dryer vent, homeowners’ can empty the lint trap at the clothes dryer with every use. It’s also a good idea to check the vent at the exterior of the home. Simply lift the louver, look into the vent. In the photo above, you can see there is a plastic cage that shouldn’t be there because it stops the excess lint from flying out. Dryer vent safety is an important aspect of owning a home, and proper maintenance goes hand in hand.

Make sure the duct doesn’t get crushed when you push the dryer back into position! To ensure there is proper airflow from the dryer to the exterior, don’t crush the vent pipe! A lot of people use the flimsy, flexible, foil or plastic type vent ducting for the dryer and these are subject to crushes and kinks.  Especially at turns and directly behind the dryer, since there isn’t much room work there normally! Instead of just bending it around, use a rigid 90 degree elbow that won’t restrict the flow of air.

Vertical runs of dryer ducting can cause problems, and if you have a vertical run you may want to install a booster fan for the vent duct to make sure that the hot, moist air gets to where it needs to go…. and that’s to the EXTERIOR!

It’s important to make sure the connections are tight and sealed so that same air doesn’t escape somewhere else where it isn’t supposed to be…. and that’s in a wall/ceiling/crawlspace!!!

National Requirements

The recommendations outlined below reflect International Residential Code (IRC) SECTION M1502 CLOTHES DRYER EXHAUST guidelines:

M1502.5 Duct construction.
Exhaust ducts shall be constructed of minimum 0.016-inch-thick (0.4 mm) 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 or fastening means which extend into the duct.


This means that the flexible, ribbed vents used in the past should no longer be used. They should be noted as a potential fire hazard if observed during an inspection.
M1502.6 Duct length.
The maximum developed length of a clothes dryer exhaust duct shall not exceed 35 feet from the dryer location to the wall or roof termination. The maximum length of the duct shall be reduced 2.5 feet for each 45-degree (0.8 rad) bend, and 5 feet for each 90-degree (1.6 rad) bend. That maximum length of the exhaust duct does not include the transition duct.

M1502.2 Duct termination.

Exhaust ducts shall terminate on the outside of the building or shall be in accordance  with the dryer manufacturer’s installation instructions. The ducts shall terminate not  less than 3 feet in any direction from openings into buildings.

Exhaust duct terminations shall be equipped with a backdraft damper.  Screens shall not be installed at the duct termination.



Proper Size

The vent duct must be properly sized.

M1502.3 Duct size.
The diameter of the exhaust duct shall be as required by the clothes dryer’s listing and the manufacturer’s installation instructions.
Look for the exhaust duct size on the data plate.
M1502.4 Transition ducts.
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 UL 2158A.
Required support for lengthy ducts is covered by the following section:

M1502.4.2 Duct installation.
Exhaust ducts shall be supported at intervals not to exceed 12 feet and shall be secured in place. The insert end of the duct shall extend into the adjoining duct or fitting in the direction of airflow. Duct joints shall be sealed in accordance with Section M1601.4.1 and shall be mechanically fastened. Ducts shall not be joined with screws or similar fasteners that protrude more than 1/8-inch into the inside of the duct.

Typically, the inspector may not know each specific manufacturer’s recommendations or local codes and may not be able to confirm the dryer vent’s compliance to them, but will be able to point out issues that may need to be corrected.

Clothes dryer fire safety outreach materials › prevention › outreach › clothes_dryers

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