Dryer Vents
about 14,000 dryer fires per year.
Perhaps 3000 of these result in house fires.
The major cause of dryer fires is lint trapped in the vent pipe ignited by the escaping heat. Many of these fires are the result of by plastic vents. These flexible plastic vents made of a plastic film assembled around a wire frame, may be occasionally suitable for making short connections between a dryer and the vent connection. However, they should never be used to send air from exhaust vents or dryers through attics or crawl spaces. The plastic will eventually fail. And if more than a few feet long, it will clog and become a fire hazard as the dryer heats. UL-approved smooth metal vents are safer. A plastic dryer vent can be replaced easily by the owner. Avoid the thin metal foil pipes. Their ribbed interiors snag lint. Rigid pipe fittings should be secured with duct tape. Sheet-metal screws may snag lint.
Four inch diameter dryer vent pipe should be no longer than 25 feet (some codes allow only 14′, allowing up to two 90 degree elbows). When calculating the 25′ length, subtract 5′ for each 90 degree elbow. For example, a dryer with a 6′ vertical pipe that is connected to a pair of elbows should have a horizontal pipe no longer than 9′. Longer 4″ pipes should be replaced with 5″ pipes. Some manufacturers do not allow their dryers to discharge to a vent that is more than a certain distance above the unit. Failure to follow the recommendation could be a fire hazard. Consult the manufacturer for recommendations.
Dryer vents installed in cold climates should be provided with insulation if the vent passes through an unheated space. Without the ventilation, water vapor may condense inside, freeze, then block the airflow when the dryer is next used, causing a fire hazard. Dryer vents should never discharge into attics, foundation crawl spaces, wall cavities, chimneys, etc. The entire system should be cleaned once each year.
Dryer through-the-wall vents should be provided with a tight-fitting damper (such as a flap) so that air infiltration can be minimized. These flaps also help prevent winds from blowing lint back into the pipe, perhaps clogging the pipe (a fire hazard). Dampers that don’t close may need lint removed or may need oil. If bent or broken, the vent must be replaced.
Chet Riley is the Owner/Proprietor of CENTENNIAL Home Inspections. For any questions regarding home inspections, please call Chet at 585-293-2278. Or e-mail him at criley1@rochester.rr.com. Further information can be obtained at http://www.centennialhomeinspections.com/.