1 Scope

1.1 These tests are intended to determine the fire resistance of grease duct enclosure assemblies. These requirements limit the combustibility, the surface flammability, and the smoke generation potential of the coverings used to enclose the grease duct. In addition, these requirements evaluate the effectiveness of the combination of the grease duct and the enclosure as a fire rated enclosure system and through penetration firestop system, as well as the enclosure's effect on the grease duct.

1.2 The fire endurance ratings for grease duct enclosure assemblies are intended to register performance during the period of fire exposure and are not intended to be interpreted as having determined the acceptability of the grease duct assembly for use before or after fire exposure. The intent of these methods is to develop data to assist others in determining the suitability of the grease duct assembly where fire resistance is required.

1.3 These requirements are intended to evaluate the ability of grease duct enclosure assemblies specified in 1.1 to contain an internal fire or repel an external fire during predetermined test exposures. The test evaluates the grease duct assembly's resistance to fire, heat, and to a hose stream.

1.4 Requirements covering the construction and performance requirements of proprietary grease ducts are contained in the Standard for Grease Ducts, UL 1978. All ducts, both proprietary and non-proprietary, shall comply with installation requirements of the Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations, NFPA 96, and the International Mechanical Code.

1.5 Under these requirements a grease duct enclosure assembly is subjected to standard internal and external fire exposures controlled to achieve specified temperatures throughout a specified time period.

1.6 During the internal fire exposure, one of two installation condition methods shall be selected to measure temperatures near or on the surface of the grease duct enclosure material away from the grease duct. One method of temperature measurement is intended for all installations except for installations within non-ventilated combustible enclosures. The second method of temperature measurement is intended for installations within non-ventilated combustible enclosures.

1.7 These exposures by themselves are not intended to be representative of all fire conditions; conditions vary with changes in the amount, nature, and distribution of fire loading, ventilation, compartment size and configuration, and heat sink characteristics of the compartment.

1.8 These requirements cover the measurement of the transmission of heat through the grease duct assembly and the passage of heat and gases hot enough to ignite cotton waste.

1.9 These requirements provide a relative measure of fire performance under these specified fire exposure conditions. Any variation from the construction or conditions that are tested, such as method of assembly and materials, is not within the scope of this test method.

Summary of Topics

This New Edition of UL 2221 includes editorial revisions such as reference updates, re-organization of sections, renumbering, and pagination. These revisions are considered to be non-substantive and not subject to UL's STP process.