Every single year there are 15,000 house fires caused by clothes dryers according to the National Fire Protection Association.
Why do most dryer fires occur? Lack of maintenance and improper installation.
The lint that is produced from drying clothes is highly flammable. When it gets trapped in the dryer vent it blocks the vent and becomes a fire hazard.
Dryer Vent Installation
Dryer vents have three sections. The transition duct and the exhaust duct at the interior, and the dryer vent cover at the exterior. These three sections create what is commonly known as the dryer vent.
The Dryer Exhaust Duct
The exhaust duct is the portion of the vent that penetrates the wall and goes outside. It also connects to the transition duct when there is one.
The International Residential Code (IRC) says the exhaust duct should meet the following standards:
be composed of rigid metal
have a 4 inch diameter
have a smooth interior finish.
The IRC also states the maximum length of the exhaust duct should be 35 ft. That length is also reduced 5 ft for every 90 degree angle and 2.5 ft for every 45 degree angle.
The IRC also gives manufacturers leeway to override the 35 ft maximum length and most do. Powered vents are also an option when the vent needs to run for an extended length.
Some GE models are approved to have over 100 ft of exhaust duct, unfortunately there is no standard. Additionally the length of the exhaust duct is measured from dryer vent hood to the transition duct connection, so you can ignore the transition ducts length in this calculation. Check out this chart to see maximum lengths for several manufacturers:
The purpose of the vent cover to prevent drafts and critters from entering through the dryer vent. To accomplish this the vent cover should have a back-draft damper. Essentially a hinged or slotted cover that opens when the dryer blows air through the vent.
DRYER VENTS SHOULD NEVER HAVE SCREENS OR CAGES.
Did you catch that?
One more time for everybody in the back…
Dryer vent covers, the outside part of the vent, should never have screens or cages of any kind. They are excellent at trapping lint and creating fire hazard conditions. This is one of the most common problems home inspectors see with dryer installations.
A proper dryer vent cover
No. No. No. Improper Screened Vent
Dryers should be maintained regularly to prevent unsafe conditions.
Lint traps in the unit should be cleaned after every use
Check the vent cover every few months to make sure it is free of blockage, clean out any lint
Remove and clean (or replace) your vents exhaust duct and transition duct annually
Even properly installed dryer vents, when not cleaned regularly can end up looking like this:
Legal Stuff: Any references to code are to IRC. Check with your jurisdiction to see local regulations which may differ. Homeowners should never perform repairs or maintenance that they are unqualified to perform, and should consider when they may be putting the safety of themselves or others at risk.
Scott Brown is a New York state licensed home inspector. He is an alumnus of Syracuse University and has worked in the construction/inspection industry for more than 10 years. He grew up working on remodeling projects around the house with his dad, much to his displeasure at the time. Scott is the owner of Brightside Home Inspections in Syracuse, NY.