PVC piping, while used frequently in residential and commercial construction for venting forced air, gas furnace vapors (both hot and moist) is not an acceptable material for dryer vents due exclusively to its combustibility factor.
Accumulated lint in any piping system (metal, PVC, Vinyl etc) is a combustible material that can and does frequently catch fire.
A PVC pipe will burn and melt helping to spread the fire.
A metal pipe will not burn or melt until and unless the fire reaches extreme temperatures.
Hardin County Planning and Development Commission Domestic Clothes Dryer Ducts. (IMC 504.6) “Exhaust ducts for domestic clothes dryers shall be constructed of metal and shall have a smooth interior finish. The exhaust duct shall be a minimal nominal size of 4 inches in diameter. http://www.hcpdc.com/pdf/Dryer%20Vent%20Requirements.pdf
Topical Fire Research Series Volume 7, Issue 1 / January 2007 Clothes Dryer Fires in Residential Buildings
The exhaust pipe should be as short as possible and have limited bends to allow for adequate airflow.
The American Household Appliance Manufacturers Association (AHAM) recommends the use of UL- listed rigid aluminum or steel duct or spiral-wound aluminum flex hose, NOT white vinyl hose. http://www.usfa.dhs.gov/downloads/pdf/tfrs/v7i1.pdf
The Association of Home Appliance Manufacturers
The installation and maintenance of clothes dryers are an important part of ensuring that the appliance performs as designed. The Association of Home Appliance Manufacturers (AHAM) has reviewed many of the building codes used across the U.S. to ensure that the installation of clothes dryers is in accordance with the manufacturer’s instructions.
AHAM, on behalf of its home laundry manufacturers, submitted comments to the 1999 edition of the National Fuel Gas Code (ANSI Z223.1/NFPA 54) to specify that exhaust and transition vents shall not be constructed of coiled-wire foil or plastic material and that vents be installed in accordance with the clothes dryer manufacturer’s installation instructions. AHAM recommends that clothes dryer vents be constructed of rigid sheet metal or corrugated semi-rigid sheet metal material. http://www.aham.org/ht/a/GetDocumentAction/i/859