The Clothes Dryer Exhaust System

---

The Dyer Vent Duct 

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

Some factors are:        

• The type of material or clothing being dried.
• Kinked or crushed transition connector, usually caused by pushing the dryer too far back toward the wall.
• Pet hair.
• Bird or rodent nest.
• Lack of regular/proper maintenance.
• The length of the exhaust vent and the number of turns it makes. (Each 90 degree turn is equal to an additional 5 feet.)
• Regular cleaning of dryer's lint filter.
• Limited air intake due to confined space or obstruction of the air intake area.
• Damaged or obstructed outlet covers. Outlet cover damper is stuck closed from lint buildup.
•  Outlet cover damper is painted or stuccoed closed.
• Poorly designed rooftop outlet covers which collect lint, blocking airflow . Because maintenance was not considered when installed, this type must be removed and repaired or replaced by a roofer.
  

These are but a few of the factors and dryer exhaust vent systems should be professionally cleaned. Most systems should be cleaned annually however some systems will need to be cleaned more frequently in order to provide you with safe, efficient, clothes drying operation. The larger your family and the more you use your dryer, the more often it should be cleaned.       

1. The dryer exhaust vent must be at least 4 inches in diameter and as large as the transition duct and dryer outlet.
   
2. The  dryer's transition duct, which runs from the rear of the dryer to the  exhaust vent, should be made of metal or UL listed for that application.  Plastic is not recommended. In case of fire, plastic will not contain  the fire but add to it.
   
3. Dryer  exhaust vent systems that are concealed in walls or through attics must  be rigid metal duct pipe, aluminum duct pipe, UL listed for this  purpose and approved by the local building and/or safety codes.
   
4. The dryer exhaust vent system shall be independent of other venting systems and terminate outdoors.
   
5. The termination outlet should have a back-draft damper.
   
6. Unless  permitted by the dryer manufacturer and local building and safety  codes, the total length of the dryer exhaust system should not exceed 25  feet. Each 90-degree elbow is equal to 5 feet of that length.
   
7. 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.
   
8. Exhaust  vent pipe joints should be installed so the male end of the pipe is  installed in the direction of the 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.
   
9. The termination vent should be checked for airflow and cleaned frequently.
   
10. The area around the dryer, rear of the dryer and intake grills should be cleaned and/or vacuumed on a regular basis.
    
11. With  a clean exhaust vent system, you should make a note of the amount of  actual time and the dryer's settings, the dryer takes to dry a normal load . Every couple of months, compare that time to how long your  dryer takes to dry a normal load. If that comparison exceeds 1/3 of the  original test, it is time to have the dryer vent system professionally cleaned.
    
12. If  you have a gas clothes dryer, you should install a carbon monoxide  detector for your protection in case of a blockage in the dryer exhaust  system. 
    
13. The use of an indoor dryer vent is NOT recommended. 
    

The  National Fire Protection Association recommendation is to have your  dryer vent professionally cleaned once a year or more frequently if your  dryer is taking longer to dry a normal load. Adjust the frequency if it  is taking your dryer longer to dry. (See #11 above.)