The Dryer Exhaust Vent

Please remember that airflow and lint buildup in the transition duct and dryer exhaust system depend on many factors.  

Some factors are: 

• type of material or clothing dried

• pet hair

• lack of regular/proper maintenance

• length of the exhaust vent

• regular clearing of dryer's lint filter

• limited air intake due to tight home or lack of makeup air  

These are but a few of the factors all beyond manufacturer's or our control.  Some systems will need to be cleaned more frequently than others to provide you with a safe, reliable, and trouble-free clothes drying operation.

• The dryer exhaust vent must be at least 4" in diameter and as large as the transition duct and dryer outlet.

• The dryer's transition duct, which runs from the rear of the dryer to the exhaust vent, should be of metal or UL listed for that application.  Plastic is not recommended, in case of fire it will not contain the fire but add to it.

• Dryer vent exhaust systems that are concealed in walls or through attics must be rigid metal pipe, aluminum pipe, UL listed for this purpose, or approved by the local authority having jurisdiction.

• The dryer vent exhaust system shall be independent of other venting systems and terminate outdoors.

• The outside termination vent should have a flapper or back-draft damper.

• Unless permitted by the dryer manufacturer, the total length of the dryer exhaust system should not exceed 25 feet.  Each 45-degree elbow shall count as 2-1/2 feet of that length.

• Ducts and exhaust vent joints should be secured with metal foil tape, not screws or rivets that may collect lint inside the exhaust vent, reducing airflow.

• Exhaust vent pipe joints should be installed so the male end of the pipe is installed in the direction of airflow.  This also reduces the chances of lint catching on the pipe joint and reduces turbulence in the pipe, both of which will reduce airflow.

• The termination vent should be checked for airflow and cleaned every couple of months.

• The area of the dryer, rear of the dryer, intake grills, transition duct, and exhaust vent inlet should be cleaned and/or vacuumed every couple of months by the owner.

• You should dry 8-10 towels and make a note of the amount of towels, actual time to dry in minutes, and dryer settings.  This will establish a base time that you can use for comparison.  Tape them in an inconspicuous place and repeat this every few months when convenient.  When the time comparison exceeds 1/3 of the time it is time to clean as instructed above or have the Dryer Exhaust Vent system professionally cleaned.

• If you have a gas clothes dryer, you should have or purchase a carbon monoxide detector for your protection in case of a blockage in the Dryer Exhaust System.