House fires caused by dryers are far more common than are generally believed. Most of these incidents occur in residences and are the result of improper lint clean-up and maintenance. Fortunately, these fires are very easy to prevent.
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. Some heavy garment loads can contain more than a litre of water that will become airborne water vapour and leave the dryer and home through an exhaust duct, more commonly known as the dryer vent.
A vent that exhausts moist air to the home’s exterior has several requirements:
- It should be connected. The connection is usually behind the dryer but may be beneath it. Look carefully to make sure it’s connected.
- It should not be restricted. Dryer vents are often made from flexible plastic or metal duct, which may be easily kinked or crushed when 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 elbows are available which are 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.
- One of the reasons that restrictions are a potential fire hazard is that, along with water vapour 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 vapour, which then accumulates 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.
Problems & Tips
If your dryer vent terminates in the subfloor or roof void, it can deposit moisture there, which can encourage the growth of mould, wood decay, and other structural problems. The vent may also terminate just under the attic ventilators. This is also a defective installation. Make sure your dryer vent terminates at the exterior and away from any doors and windows so that damp, exhausted air won’t re-enter the home. Also, the end of the dryer vent should have a free-moving damper installed to keep out birds and other pests that like to build nests in this warm environment. If you find a screen, this is a defective installation because a screen can block lint and other debris, causing it to accumulate and leading to a house fire. If it’s safely accessible, make sure your dryer vent is unobstructed and that the damper works properly.
