Statistics and Implications
- Dryer exhaust fires now surpass creosote (chimney) fires in frequency on a national level. In 1998, the most recent statistics available, the Consumer Product Safety Commission reports that over 15,600 dryer fires occurred killing 20 people, injuring 370 more and causing over $75.4 million in property damage. According to the CPSC, in most of these cases the culprit was lint getting into the machine’s heating element, sparking and fueling a fire. In response to this growing trend, many dryer manufacturers now employ a device that shuts the appliance down when airflow is obstructed. However, these safeguards are subject to wear and have been known to fail. Not surprisingly, some fire departments and insurance companies now require that dryer vents be inspected and cleaned regularly.
- With gas dryers, there is also concern of carbon monoxide (CO) poisoning. Since lint and flue gases use the same avenue of exit from the house, a blocked vent can cause CO fumes to back up into the house. These fumes are colorless and odorless and they can be fatal. Low-level CO poisoning mimics flu symptoms (without the fever): headache, weakness, nausea, disorientation and deep fatigue. At higher levels, occupants can fall asleep, lapse into a coma and die.
Anatomy of a Dryer Fire
Dryer fires usually start beneath the dryer when the motor overheats. Overheating is caused by a build-up of lint in the duct that increases the drying time and blocks the flow of air, just like cholesterol in your arteries can build up and block the flow of blood to your heart. Naturally, any lint that has collected under the dryer will burn and the draft from the dryer will pull that fire up into the duct. Since the duct is coated or even blocked with lint, many times a house fire results. Other contributing conditions may include failure of the thermostat and limit switches in the dryer, lint inside the dryer, a missing or damaged lint screen, a crushed hose behind the dryer, or a bird’s nest or other debris blocking the vent.
Higher Risk Situations
- Residential dryer vent lengths may not have an equivalent length greater than 25 feet. Five additional feet for each 90-degree bend must be added to the actual physical length to compute the vent’s equivalent length. This will determine the vent’s actual resistance to the airflow.
- Homes with larger families or where dryers are used heavily are at greater risk.
- Flexible plastic duct is no longer code-approved for clothes dryers. It is normally one of the first things burning lint will ignite, having been shown to flame in as little as 12 seconds. Lower cost and high flexibility often make it attractive to unadvised homeowners installing their own machines.
- Flexible duct made of thin foil is not recommended for clothes dryers. Replace plastic or foil, accordion-type ducting material with rigid or corrugated semi-rigid metal duct. Most manufacturers specify the use of a rigid or corrugated semi-rigid metal duct, which provides maximum airflow. The flexible plastic or foil type duct can more easily trap lint and is more susceptible to kinks or crushing, which can greatly reduce the airflow.
Warning Signs of Potential Fire Hazards
- Dryer is still producing heat, but taking longer and longer to dry clothes, especially towels and jeans.
- Clothes are damp or hotter than usual at the end of the cycle.
- Outdoor flapper on vent hood doesn’t open when dryer is on.
Additional Benefits to Dryer Vent Cleaning
- Allows your dryer to operate more efficiently, using less energy and saving you money.
- Protects your dryer from excess wear and premature death.
- Helps clothes dry faster—a time savings for busy families.
- Reduces excess household dust and humidity
- Helps preserve clothing, as the life of many fabrics is damaged by excessive high heat.
Most vents need cleaning every two to three years. Some dryer vents need attention more often. If it is the first time that a dryer vent has been cleaned, having it re-checked again in a year can help to make a reasonable judgment. Determining factors include:
- How heavily the dryer is used
- How long the vent is and the materials used. Shorter vents usually blow better.
- The age and type of dryer used. Full size dryers blow better than smaller stack dryers or older dryers
- The design of the vent. Those with a lot of turns and elbows blow worse and build up more lint.
U.S. Consumer Product Safety Commission