In 2021, U.S. fire departments responded to a structure fire every 65 seconds, according to the National Fire Protection Association.1 Fire safety is a critical aspect of building design and construction, and one crucial component to safeguard people and property is the implementation of fire doors and assemblies. These play a vital role in containing and controlling the spread of fire and smoke within a building, and UL Standards & Engagement has had safety standards guiding the safe development and use of these products in publication for 120 years.
In this article, we will explore the significance of the UL 10 series of standards for fire doors and assemblies, and highlight their impact on the fire service. We will discuss their history and purpose, their requirements for construction and testing, and how they aid firefighters in life-saving operations.
The UL 10 series of standards includes the following:
- UL 10A, Standard for Tin-Clad Fire Doors
- UL 10B, Standard for Fire Tests of Door Assemblies
- UL 10C, Standard for Positive Pressure Fire Tests of Door Assemblies
- UL 10D, Standard for Fire Tests of Fire-Protective Curtain Assemblies
History
In 1903, Underwriters Laboratories published its inaugural standard, ‘Tin Clad Fire Doors’, marking the genesis of the organization’s enduring commitment to the fire-door industry and paving the way for a rich legacy of involvement in this critical field. Over the 120 years since its first publication, the Standard has seen many revisions advancing fire-door technology by setting requirements for material construction, testing and performance.
One of the tests from the early days of this Standard that is still in practice today is the hose stream test. During this test, the doors are exposed to fire conditions in a controlled environment to achieve specified temperatures, then subjected to a hose stream application. The purpose and intended outcomes of this test are explained later in this article.
Purpose of standards for fire doors and assemblies
Fire doors and assemblies tested to UL 10B and UL 10C are specifically designed to prevent the spread of fire, smoke and toxic gases within a building. Their primary purpose is to compartmentalize areas and create fire-resistant barriers that restrict the movement of flames and smoke through a structure during a fire incident. Their secondary purpose is to provide a dependable form of egress in emergency situations. These doors are strategically installed in areas where fire compartmentation is critical, such as stairwells, corridors, elevator shafts and fire-rated walls.
Fire doors and assemblies that conform to the standards in the UL 10 series undergo rigorous testing procedures to evaluate their fire resistance and ability to mitigate the passage of flames, smoke and gases, as defined by the standards. During these tests, the doors and assemblies are subjected to intense heat conditions for a specified duration to simulate a real-life fire scenario. The doors are evaluated for criteria such as integrity (the ability to resist the passage of flames and hot gases), stability (the ability to maintain structural integrity) and insulation (the ability to limit temperature rise on the non-fire side).
UL 10B and UL 10C focus specifically on the fire-related tests for the door assembly. Both standards evaluate the structural integrity and stability of the door assembly. However, UL 10C is the more rigorous of the two as it applies additional pressure forces throughout the duration of the fire exposure test. Companies that test products to UL 10B or UL 10C tend to prefer certification of conformance to UL 10C due to these enhanced requirements because it signals to the consumer that the product can withstand extreme fire-related occurrences while maintaining structural integrity.
Construction and components
UL 10 Standards for fire doors and assemblies require the products to be constructed using materials that exhibit excellent fire-resistance properties. The average fire-resistance rating of a steel door intended for human egress is three hours, while the average fire-resistance rating of a wood door is 90 minutes. The Standards require that the doors must consist of a fire-rated core material, such as mineral fibreboard or composite wood core, and must be encased in fire-rated facings, such as steel or composite materials. Additionally, fire-rated glazing may be incorporated into the doors to allow visibility and enhance evacuation efforts while maintaining fire resistance.
UL 10B and UL 10C contain construction requirements stating these products must be equipped with fire-rated frames and hardware including hinges, latching mechanisms and closing devices that are equal to or greater than the rating of the door. These components are specifically designed to withstand high temperatures, maintain their integrity and minimize the instances of flaming on the door assembly during a fire event.
![Fire-Door-Side-by-Side.jpg] Hose Stream Test, 1915 (top) and present day (bottom). (©ULSE Inc.)](https://ifpmag.com/wp-content/uploads/2023/08/Fire-Door-Side-by-Side-1.jpg)
The Standards also require testing such as a hose stream test on the entire fire-door assembly (including door, frame and wall). As mentioned earlier, this test is performed by exposing a fire-door assembly to fire conditions in a controlled environment and then subjecting it to a hose stream application, which simulates horizontal impact loads. These loads probe the entire area of the fire assembly searching for weaknesses that result from the fire exposure. This testing is critical, as the fire exposure within a building can cause falling debris (such as structural members) or flying debris (such as that resulting from explosions in industrial plants) to contact the assembly and create an additional load. The hose stream application assesses the capability of an assembly to withstand impact loads while retaining its structural integrity, regardless of the source of impact.
Impact on the fire service
The UL 10 series of standards for fire doors and assemblies helps to guide the development and implementation of safe products that have a significant impact on fire service operations. These doors provide critical time for firefighters to conduct search and rescue operations, evacuate occupants and control the spread of fire. The presence of properly installed and maintained fire doors allows firefighters to focus their efforts on specific areas, reducing the risk of fire propagation and increasing the chances of successful firefighting operations.
Moreover, fire doors enhance the safety of occupants by providing designated fire exits and escape routes. During a fire incident, these doors prevent the rapid spread of smoke and toxic gases, allowing individuals to evacuate safely, while also reducing their risk of smoke inhalation and asphyxiation. For those unable to evacuate, fire doors can slow the spread of heat, flames and smoke – providing crucial extra time for first responders to perform rescue operations.
Fire doors also contribute to the effectiveness of fire-suppression systems by helping to confine fire and smoke to the source area. By compartmentalizing the fire, these doors limit the oxygen supply, helping to control the growth and intensity of the fire until firefighters arrive on the scene.
It is important to note that the effectiveness of fire doors relies on proper installation, regular maintenance and adherence to safety protocols. In 2019, the Fire Door Inspection Scheme (FDIS) in the U.K. found that 76% of the fire doors it inspected were condemned as not fit for purpose, indicating that maintenance had not been conducted since the previous inspection.2 The fire service plays a crucial role in promoting fire-door awareness, conducting inspections and ensuring proper operation. Firefighters are trained to recognize and assess fire-door conditions during fire incidents, allowing them to make informed decisions regarding access, ventilation and fire control.
Conclusion
Standards for fire doors and assemblies serve as critical elements in fire safety for buildings. They provide essential barriers helping to prevent the spread of fire and smoke, protect occupants and assist the fire service in life-saving operations. A thorough understanding of the purpose, construction, safety standards and impact of fire doors, building owners and the fire service can work together to ensure these doors provide optimal fire safety and protection.
If you would like to get involved in the development and ongoing maintenance of the UL 10 series of standards for fire doors – or any of our 1,500 published standards – please visit ULSE.org/get-involved.
References
1. Hall, S. Evarts, B. ‘Fire Loss in the United States During 2021’ (2022). National Fire Protection Association (NFPA). https://www.nfpa.org/~/media/Files/News%20and%20Research/Fire%20statistics%20and%20reports/US%20Fire%20Problem/osFireLoss.ashx
2. Sexton, R. ‘Three quarters of fire doors fail inspections according to FDIS’ (2022). https://www.ifsecglobal.com/fire-news/three-quarters-of-fire-doors-fail-inspections-according-to-fdis/amp/
About the Author
Wil Fletcher
Wil Fletcher is a Senior Project Engineer for UL Standards & Engagement. He serves as a technical lead for fire-related UL and ULC standards, and he provides technical support to American and international staff in fire protection. Prior to UL Standards & Engagement, Wil served as a career firefighter for more than 10 years, ascending to the rank of chief officer.
Mariah Dixon
Mariah Dixon is a Project Engineer for UL Standards & Engagement. Mariah serves as a technical lead to mechanical-related UL and ULC standards, and she provides support to American and international staff over various standard categories. Mariah was previously a Project Engineer with UL Solutions for five years, during which she tested and certified fire-containment products to various UL, International Organization for Standardization, and NFPA standards.
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