UL 103 for Factory-Built Chimneys

About UL Listings

Founded in 1894, UL Solutions (previously called Underwriter’s Laboratories, Inc.) is a third-party certification company. Its stated mission is to help create “a safer world,” supporting “the production and use of products which are physically and environmentally safe.” To meet this goal, they rigorously examine devices, systems and materials in their testing labs, providing specifications and guidance for products, equipment constructions and systems. Their UL mark is the single most accepted certification mark in the United States, appearing on 22 billion products annually. There are more than 1,500 different UL Standards, and each number represents a different application and level of protection.

UL 103: The UL Standard for Safety for Factory-Built Chimneys for Residential Type and Building Heating Appliances.

The UL 103 Generator Exhaust System standard covers a factory-built chimney intended for “venting gas, liquid and solid-fuel fired appliances in which the maximum continuous flue-gas outlet temperatures do not exceed 1000˚F.” These chimneys can be installed inside or outside of a building. Although they are rated to continually perform in temperatures up to 1000ºF, they are tested to withstand temperatures as high as 1700ºF (927º C).

While it might seem obvious that a fire-rated chimney is critically important, only some companies manufacture them, as qualifying for a UL listing can be costly and time-consuming. When a product does not receive one, it may pose a fire risk. There are more than 25,000 chimney fires a year (business and residential), many of which lead to structure damage, injuries and even fatalities. That number would be significantly sliced if all chimneys were UL 103 listed.

UL 103 Generator Exhaust System Testing and Requirements

The standard for the UL 103 Generator Exhaust System lists the recommended requirements for materials used, assembly and even a myriad of details on specific components, including chimney caps, firestop spacers and joints. They also list several tests that UL performs and the requirements for passing them. A list of those tests alone shows the comprehensiveness of the testing, as well as the harsh requirements needed to earn a UL listing. Those tests include:

• Thermal Shock Test
• Temperature Tests for 1000˚F, 1400˚, 1700˚ and 2100˚ Flue Gases
• Positive-Pressure Applications Test
• Draft Test
• Vertical Support Test
• Strength Tests (Impact Tests, Longitudinal Force Tests, Chimney-Joint Load Tests and others)
• Wind Load Test
• Attic Insulation Shield Ventilation Opening test
• Rain Test
• Crushing Test of Nonmetallic Flue-Gas Conduit
• Resistance to Action of Acids Test
• Freezing and Thawing Test
• Cemented-Joint Test
• Sulfuric Acid Extraction Test

The Certainty of UL Listed Safety

A UL listing is not a one-time event. UL Solutions performs quarterly inspections, appearing at a facility unannounced to examine parts, conduct tests, measure dimensions and even check product labels for accuracy. If UL uncovers a violation, it can completely halt production of that product.

At Schebler, we’re proud to have been UL certified since 1994 and have never received a single major violation. This certainty is one of the key reasons we’re the unquestioned leader in providing the finest prefabricated chimney and exhaust systems.

Contact us to learn more.