Ahmed Amin, P.E.
Dryer Venting Safety
Updated: Dec 27, 2020
Did you know that approximately 2,900 home cloth dryer fires are reported each year. Out of all the reported fire (34%) is due to failure to clean the dryer. You are at higher risks of having a clothes fire if you do not clean your lint filter and dryer vents. Here are some things you should consider and apply to minimize the occurrence of a dryer fire.
Dryer Vent Types
First, to have a safe dryer you need the correct type of dryer vent. Any dryer duct used should be 4" in diameter. There are 4 commonly found vents; which are:
1. Flexible Vinyl Duct
2. Rigid Metal Duct
3. Flexible Foil Duct
4. Semi Rigid Aluminum Duct (UL215A Listed)
However, the only two acceptable and safe ducts listed above, are the semi-rigid aluminum and rigid metal duct to sustain proper air flow and drying time. Although the other two ducts are sold in many common hardware stores, they can more easily trap lint and are more prone to damage. Additionally, be cautious in crushing or bending semi-rigid duct work when having it installed, as this can constrict the removal of lint.
Here is an image showing you the difference between a foil duct and semi-rigid duct.
Dryer Vent Duct Run
Selecting the correct dryer vent is the first step in having a safe dryer connection. What about the actual installation? Most building codes and manufacturers require a "straight" run of 25 - 35 ft. or less. However that does not apply if you are adding elbows or bends in the mix. For every elbow you apply a 5 ft. length reduction (i.e. 2 bends - max length should be reduced to 15 ft.). It is imperative you check the dryer manufacturers manual that comes with your specific dryer model. As an extra incentive, if you reduce the exhaust duct you will decrease the dryer times and overall energy cost, increase the dryer life, and accumulate lint less reducing potential fire hazard.
Here is an example of how NOT to vent a dryer from a recent Home Inspection
Dryer Vent Termination
Ensure you install a proper termination cover without a screen. Screens impede proper air flow. The dryer should terminate penetrating an exterior wall and NOT through a window. The three type of acceptable dryer vent hoods include, angled, box, and louvered.
Here is a figure showing you the different hood covers (Image Credit - Whirlpool Corp.)
It is absolutely important for you to clean out your dryer vent periodically (minimum of once) a year and always clean your lint tray before and after you use your dryer. Look behind the dryer and see if there is any lint building up on the floor. and clean that up as well. This may be a sign that the lint is escaping the dryer duct and you should inspect for any penetrations. Inspect the exterior hood of your dryer vent and ensure the exterior hood flap is functioning and not damaged.
If you notice your dryer is not fully drying clothes in full cycle this may be a sign that your exhaust is clogged and should be cleaned out. Remember, this will waste more gas/power and become detrimental on your dryer overtime (shortening lifespan).
Other Safety Tips
Here are some additional best practices:
1. Do not overload a dryer with wet clothes and do not leave a dryer running when you are not home.
2. Do not dry any items made of foam, rubber, or plastic, all of which can melt and cause a fire.
3. Do not place clothes or fabric soiled with a flammable substance, such as gasoline, cooking oils, grease, or oil, in a dryer.
4. If you have an electrical dryer; ensure it is plugged into an outlet suitable for its electrical needs (typically 220/240 V). A dryer should never be plugged into an extension cord.
5. If you have a gas dryer; ensure there are no gas leaks and connections are made tight.
6. Maintain 4 in clearance around the back of the dryer where the duct work terminates the dryer.
7. Booster fans are not recommended by most manufacturers, but should be used if duct is longer then 35 ft. for proper exhaust airflow.
8. You can higher professionals to inspect and clean out your dryer duct.
Ensure you are using the correct semi rigid or rigid duct work for your dryer (UL Listed 215A). It is recommended to keep the duct as short as possible with minimal to no bends if possible. Do not forget to clean the lint tray and periodically inspect and clean your dryer duct work. Inspect the full run and exterior portion of the dryer duct. If you notice your dryer acting funny or taking longer to dry cloth then this is a sign there is something wrong. As with everything apply common sense and better to be safe then sorry.