I felt I had to write and inform people about fire hazards with respect to dryers. The photo below is one I took of a project I had been hired to work on and this is the condition of the dryer venting hose I brought to my clients attention. I want to inform home owners that this is a potential fire hazard and everyone should take this seriously.
A clothes dryer vent system needs to be installed properly and maintained on a regular basis to keep the dryer operating efficiently. Improperly installed and maintained dryer vents can result in clogged dryer vents that can cause your dryer to overheat and create the potential for a serious fire.
In order for clothes dryers to function properly, they must be vented correctly. Regardless if you are diligent about checking the lint filter after every load, lint can still build up in your vent hose. Are you using the safest type of vent hose?
All local building codes now require metal ducting for clothes dryers. Ideally, you should use rigid aluminum tubing pieces between the dryer and the outside vent. This type of tubing does the best job of resisting the collection of lint in the duct. Flexible aluminum ducting is available, however, it is more prone to collecting lint inside.
If you still have white vinyl duct hose, it should be replaced immediately. It is flammable and if ignited by the dryer it will burn and cause a house fire. Aluminum vent hose is inexpensive and well worth your time and trouble to install. It may save a life.
So What Kind of Dryer Exhaust Venting Is Considered Acceptable?
I have attached a link provided by a company called The Inspection Consultant to help you find the best answer to this question including other valuable information regarding codes and guidelines.
The recommendations outlined below reflect International Residential Code (IRC) SECTION M1502 CLOTHES DRYER EXHAUST guidelines:
M1502.5 Duct construction.
Exhaust ducts shall be constructed of minimum 0.016-inch-thick (0.4 mm) rigid metal ducts, having smooth interior surfaces, with joints running in the direction of air flow. Exhaust ducts shall not be connected with sheet-metal screws or fastening means which extend into the duct.
This means that the flexible, ribbed vents used in the past should no longer be used. They should be noted as a potential fire hazard if observed during an inspection.
M1502.6 Duct length.
The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet (7,620 mm) from the dryer location to the wall or roof termination. The maximum length of the duct shall be reduced 2.5 feet (762 mm) for each 45-degree (0.8 rad) bend, and 5 feet (1,524 mm) for each 90-degree (1.6 rad) bend. The maximum length of the exhaust duct does not include the transition duct.
This means that vents should also be as straight as possible and cannot be longer than 25 feet. Any 90-degree turns in the vent reduce this 25-foot number by 5 feet, since these turns restrict airflow.