Dryer Vent Best Practices

dryer vent best practices

In this article, we discuss the best installation products and techniques to prevent dryer vent fire hazards.

According to the NFPA (National Fire Protection Agency), there are around 16,000 clothes appliance-related fires each year in the US, with most of them caused by clothes dryers. Most fires are caused by clogged ducts, filters, and vents due to maintenance neglect and improper installation.

How to Prevent Dryer Vent Fires

1. Clean the lint tray after every use

2. Make sure the dryer duct and vent are professionally installed

3. Have your dryer duct and vent professionally cleaned and inspected annually


How Dryer Vents Should Always Be Installed

All Dryer Vents should always exit to the outside

Dryer Vents should not exit into ‘bucket’ systems (see photo below), crawl spaces, basements, attics, or other indoor areas. Dryer vents should always exit to the outside.

dryer vent bucket
WRONG!! These ‘Dryer Vent Kits’ should never be used even though they are sold at big box stores and marketed for dryers. Dryer vents should always exit to the outside.
bucket type dryer vent kit.  Photo by Inspector Dustin
WRONG! Bucket-type dryer duct vent ‘kits’ are not allowed and are fire hazards even though they are marketed and sold at big box stores for this purpose

All Dryer Vents Hoods should always have a functioning damper

Dampers prevent pests from entering the duct and causing fire hazards and other issues.

metal dryer vent trim with damper or flap
GOOD! Metal dryer vent hood with damper or flap — because plastic dampers are prone to UV damage we prefer aluminum and stainless steel dryer vent hoods.

Dryer Vent Hoods should never have screens

Screens are not allowed on the dryer vent hoods because they allow the accumulation of lint. Luckily these screens are easily removed. If screens are present and lint debris has accumulated it is recommended to have the entire duct professionally cleaned.

dryer vent with screen
WRONG! Dryer Vents exits should never have screens because they can accumulate lint debris and cause fires
clogged dryer hood screen
WRONG! Clogged dryer vent hood screen. Fire hazard!

Dryer Vents Should always be 4″ smooth metal from the laundry room to the outside

Flexible ductwork should only be used between the dryer and the wall connection- these are called ‘transition ducts’ because they transition from the appliance to the vent. Flexible ductwork should never be used through or beyond floors and walls.

4 inch smooth metal duct
GOOD! 4″ Smooth Metal Ducts should always be used between the laundry room and the outside (not flexible or ‘transition’ duct)
clogged dryer duct condensation.  photo by Inspector Dustin
WRONG! Only 4″ smooth metal ducts should be used through and beyond framing. This duct is clogged and evidence of condensation was observed. Fire hazard!
flexible duct under floor framing.  Photo by Inspector Dustin
WRONG! Flexible ducts below the floor framing. Damaged and disconnected duct with a screen. All kinds of wrong. Fire hazard!

Dryer Vents should never be longer than 35 feet

The 4″ smooth metal pipe between the laundry room and the outside should never be longer than 35′. 5′ should be subtracted from the 35′ number each time a 90-degree elbow is used.

elbow
GOOD! Flame-resistant steel 90-degree metal elbow for dryer ducts. Every elbow reduces the 35′ maximum length by 5′.

Only Metal Professional Flame-Resistant connectors should be used – no Plastic connectors!

Plastic connectors, even though they are marketed and sold for dryer connections, should not be used. Only metal flame-resistant connectors should be used.

dryer vent connectors 2
GOOD! Metal, flame-resistant connectors. All connections should be secured with retaining rings/clamps.
dryer vent duct tape
GOOD! Flame-resistant and rated dryer duct tape. Dryer duct and vent seams and connections can and should be covered with this type of tape.

Best Practice Dryer Vent Connection (behind the dryer)

The best dryer vent connection is a recessed metal vent box like the one shown which helps protect the connection from damage. When it is not possible to install a recessed dryer vent box, other low-profile flame-resistant connectors can be used to protect the flexible transition ducts from damage or from disconnecting. Ideally, the dryer exits through the wall and not the floor- floor connections are more prone to damage. It is also recommended to build a ‘stop’ to prevent washers and dryers from crushing the ducts.

recessed dryer vent boxx 1
GOOD! Flame-resistant recessed metal dryer vent box helps to prevent the vents from disconnecting or becoming damaged.
dryer vent duct
Low-profile dryer vent connectors can be used to help prevent the flexible transition duct from becoming damaged or disconnected

Best Practice Transition Duct between the dryer and the wall

Flexible ducts or ‘transition’ ducts should never be longer than 8′ and should only be made of flame-resistant metal (see photographs). The first product is preferred over the second and third.

aluminum semi rigid duct
GOOD! This is a pure all-Aluminum construction product that is extremely flame-resistant and it is the most recommended type of transition duct between the dryer and the exhaust vent. Observe closely the difference between this all-Aluminum duct and the incorrect semi-plastic type below. This type is duller in color, it is semi-rigid and the rings are closer together. The product above is safer and more flame-resistant than the product below even though it is slightly more rigid.
flexible duct
NOT RECOMMENDED! (See the result of a fire in the picture below) This product looks similar to metal but it contains plastic layers. It’s typically a 4 or 5-layer product- plastic layers (PET and PVC) alternate with Aluminum layers for greater flexibility. Although they are more flexible they are not as safe as the semi-rigid all aluminum construction ducts shown above this one. These flexible semi-plastic ducts are marketed and sold for dryer ducts but they are vulnerable to combustion – especially when subjected to high voltage electricity (220-240 volts common with dryers) or extremely high temperatures. Some of these products are incorrectly marketed as ‘All-Aluminum construction’ – although they are not.
plastic dryer vent
WRONG! Plastic dryer vents are no longer allowed and are considered fire safety risks.
3 types of flexible ducts.
WRONG! 3 different types of flexible transition ducts were observed in this crawl space. Only 4″ smooth metal ducts should be used through and beyond floors and walls. Only the all-aluminum product on the right side of the photo should be used between the dryer and vent connection in the laundry room only. The semi-plastic flexible duct at the left and the all-plastic duct in the middle can catch fire and should not be used (see below)
semi plastic dryer vent fire
FIRE HAZARD! This semi-plastic dryer duct caught fire in the crawl space and nearly burned the building down. These semi-plastic ducts are four or 5-ply products that alternate plastic layers with aluminum layers for greater flexibility. With increased flexibility also comes higher fire risks.

Regularly Inspect Your Dryer Duct connection for damage or leaks

Washers and dryers often move during operation. Check behind your washer and dryer every couple of months for damage or leaks. Also, check your 4″ smooth metal exhaust vent (where accessible) and the exit (vent hood) for damage or other issues. If you observe any plastic parts or damaged or disconnected areas, contact an HVAC contractor for repairs to prevent possible fires and condensation issues.


Appliance and Vent Inspections in Asheville and WNC

Our Company, Builder Buddy Inspections & Testing, evaluates (when accessible) the dryer ducts, connections, and vents as part of our Home Inspections, Pre-sale Inspections, Commercial Inspections, and Annual Maintenance Inspections.  Dangerous fire hazards are widespread and can be prevented as part of our Annual Inspection Program. If you are within 40 miles of Asheville, call us today to set up an appointment or schedule here.

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