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Dryer Vent Safety

By
Education & Training

Clothes dryers evaporate the water from wet clothing by blowing hot air past them while they tumble inside a spinning drum. Heat is provided by an electrical heating element or gas burner. Some heavy garment loads can contain more than a gallon of water which, during the drying process, will become airborne water vapor and leave the dryer and home through an exhaust duct (more commonly known as a dryer vent).   A vent that exhausts moist air to the home exterior has a number of requirements:

  1. It should be connected. The connection is usually behind the dryer but may be beneath it. Look carefully to make sure it's actually connected!
  2. It should not be restricted. Dryer vents are often made from flexible plastic or metal duct, which may be easily kinked or crushed where they exit the dryer and enter the wall or floor. This is often a problem since dryers tend to be tucked away into small areas with little room to work. Vent hardware is available which is designed to turn 90° in a limited space without restricting the flow of exhaust air. Restrictions should be noted in the inspector's report. Airflow restrictions are a potential fire hazard!
  3. One of the reasons that restrictions are a potential fire hazard is that, along with water vapor evaporated out of wet clothes, the exhaust stream carries lint - highly flammable particles of clothing made of cotton and polyester. Lint can accumulate in an exhaust duct, reducing the dryer's ability to expel heated water vapor, which then accumulates as heat energy within the machine. As the dryer overheats, mechanical failures can trigger sparks, which can cause lint trapped in the dryer vent to burst into flames. This condition can cause the whole house to burst into flames! Fires generally originate within the dryer but spread by escaping through the ventilation duct, incinerating trapped lint, and following its path into the building wall.

InterNACHI believes that house fires caused by dryers are far more common than are generally believed, a fact that can be appreciated upon reviewing statistics from the National Fire Protection Agency. Fires caused by dryers in 2005 were responsible for approximately 13,775 house fires, 418 injuries, 15 deaths, and $196 million in property damage. Most of these incidents occur in residences and are the result of improper lint cleanup and maintenance. Fortunately, these fires are very easy to prevent.

Comments (7)

David Salvato
David Home Inspection Service Home Inspector San Bernardino - Los Angeles, CA

Eragorn Thanks for posting this blog on vent safety! We use a bore scope from time to time to really get a good picture of whats going on in the vent line.

Feb 09, 2010 02:52 AM
Robert Rauf
CMG Home Loans - Toms River, NJ

Eragorn, We use dryer lint as a fire started in Boy Scouts... Just shows how flamable it is!

A clean vent is also MUCH more efficient.

Feb 09, 2010 02:53 AM
Ian Niquette
Square One Home Inspection - Markesan, WI

Nice blog Eragorn. The dryer vent is one thing that has a very high rate of defect when it comes to the home inspection. 

Feb 09, 2010 10:52 PM
Eragorn Francis
Moose Jaw, SK
Business Owner

yes, i have found many creativly bad ways to vent a dryer, in my inspections.

thanks for all the comments.

Feb 11, 2010 05:22 AM
Not a real person
San Diego, CA

The fires are very easy to prevent, but it takes educating the home owner. Sometimes I think that if we have to have a license to drive a car, we should have a license to own a home so that people will understand just how dangerous are the places where we live.

Feb 16, 2010 02:09 AM
Stephen Kappre
KW Hometown - Mantua, NJ
Helping You Home

My boss just had a fire because of lint, and my neighbors who brought a brand new house had their exhaust clogged with crap from the builder ... so you never know!!! But that stuff is crazy flammable, as commented above, we use it to start fires all the time.

Feb 17, 2010 09:45 PM
Gita Bantwal
RE/MAX Centre Realtors - Warwick, PA
REALTOR,ABR,CRS,SRES,GRI - Bucks County & Philadel

Thank you for the post. I think we should mention in the rental leases that the dryer vent should be cleaned regularly.

Feb 17, 2010 09:53 PM