1.1 These requirements apply to venting systems, constructed of rigid metal, for venting household
electric clothes dryers and Type 1 gas-burning household clothes dryers as defined by the Standard for
Gas Clothes Dryers, ANSI Z21.5.1 and the National Fuel Gas Code, NFPA 54.
1.2 Venting systems covered by these requirements are intended to convey exhaust air containing
moisture, lint, and the byproducts of combustion from household clothes dryers to the outside atmosphere
or to an existing permanent duct provided as part of the building structure. These venting systems are
intended for use with clothes dryers that have been installed in accordance with the manufacturer's
instructions, National Fuel Gas Code, NFPA 54, National Electrical Code, NFPA 70, and state or local
codes.
1.3 These requirements do not cover flexible venting systems.
1.4 A product that contains features, characteristics, components, materials, or systems new or different
from those covered by the requirements in this Outline of Investigation, and that involves a risk of fire,
electric shock, or injury to persons shall be evaluated using the appropriate additional component and
end-product requirements to determine that the level of safety as originally anticipated by the intent of this
Outline of Investigation is maintained. A product whose features, characteristics, components, materials,
or systems conflict with specific requirements or provisions of this Outline of Investigation shall not be
judged to comply with this Outline of Investigation. Where appropriate, revision of requirements shall be
proposed and adopted in conformance with the methods employed for development, revision, and
implementation of this Outline of Investigation.
UL SUBJECT 2399-2001 history
2004UL SUBJECT 2399-2004 Outline of Investigation for Metal Venting Systems for Household Clothes Dryers (Issue 2)
2001UL SUBJECT 2399-2001 Outline of Investigation for Metal Venting Systems for Household Clothes Dryers Issue Number: 1