Based on industry meetings and discussions, it has come to UL’s attention that some within the fire door industry might benefit from a refresher on UL’s basic practices surrounding certification of special-purpose fire door assemblies.

The purpose of this bulletin is to elaborate on the critical details of the certification approach for special-purpose fire doors, UL category code GSXZ.  Special-purpose fire doors are investigated to the basic requirements of ANSI/UL 10B, Fire Tests of Door Assemblies, and may also be investigated to ANSI/UL 10C, Positive Pressure Fire Tests of Door Assemblies, when identified by the individual certification.  The UL certification for GSXZ references NFPA 80, Standard for Fire Doors and Other Opening Protectives, with the intent that these requirements are followed for the installation and maintenance of the special-purpose fire door assembly. It should be noted that NFPA 80 does reference special-purpose horizontally sliding accordion or folding doors but does not consider provisions for other types of special-purpose fire doors such as the swinging-type.

UL certification is based on testing of the full assembly, which consists of, but is not limited to, the door, door frame, hinges, latches, or other components.  When the full assembly complies with the certification requirements of GSXZ, the door manufacturer (UL file owner) obtains UL documentation used during periodic inspections that lists the mandatory components of the assembly, including manufacturer and specific model that shall be assembled in the production facility and installed in the field.  With this approach, the individual components are not considered UL certified on their own or interchangeable between door assemblies, but are considered part of the specific UL certified assembly when assembled and installed in accordance with the UL documentation.

UL’s role, once certification is established, is to provide periodic review for the appropriate manufacturing/construction of these assemblies during the follow up service inspections and to equip the authority having jurisdiction with the information necessary to enforce the field installation and utilization.  The individual components of a special-purpose fire door assembly are not intended to be substituted or replaced with alternate components, unless specified within the UL documentation and manufacturer’s installation information.  This type of certification is different than the schemes used by Swinging-Type Fire Doors, UL category code GSYX, and Swinging-Type Fire Doors, Positive-Pressure Tested, UL category code GSZN, where the door alone carries the certification and any other component, such as the frame, hardware or accessories, shall also be UL certified and can be used interchangeably.

In summary, it is important to know that special-purpose fire doors certified by UL under the category GSXZ require all components and construction details as outlined in the UL documentation to be followed to help ensure the assembly will perform as intended.  In an effort to bring more clarity to this topic, UL will be working with the industry to determine what may be done to reinforce this information within our published certifications.


Luke C. Woods
Principal Engineer – Fire Resistance and Containment