Expanding UL’s Numbering Systems

UL has a long established numbering system for Through-Penetration Firestop Systems (XHEZ) and Joint Systems (XHBN). These categories having been around for many years are are nearing the end of the available system numbers. Specifically the C-AJ-2000 series of Through-Penetration Firestop Systems and the HW-D-0000 series of Joint Systems are affected by the limited availably of the current system numbers. For example in UL’s Product iQTM database the most recently published system in the C-AJ-2000 series is C-AJ-2923 and the most recently published system in the HW-D-0000 series is HW-D-0944. Each series has 999 system numbers available to them: C-AJ-2001 through C-AJ-2999 and HW-D-0001 through HW-D-0999. In an effort to maintain continuity in numbering schemes, and to allow for further promulgation of Through-penetration Firestop Systems and Joint Systems by UL, there is a need to enhance the numbering sequence to accommodate these series running out of available numbers.


Question: Will UL change or modify existing system numbers?
Answer: No, existing system numbers will not change.

Question: What will happen when the HW-D-0000 series reaches its limit? What will happen when system HW-D-0999 is promulgated?
Answer: After HW-D-0999 is issued, the next system number that UL will issue will have five digits, instead of four. The next system number will still start with 0 (zero), followed by four digits. The 0 (zero) at the beginning of the number series indicates a dynamic head-of-wall system with a nominal joint width of less than or equal to 2 in., and this will remain the same for the new numbering sequence as well. The next system numbers will be HW-D-01001, HW-D-01002, HW-D-01003, etc.

The leading digit in the numbering sequence and its significance for the type of penetrant, size of joint etc. in each category will not change.

Question: What will happen when the C-AJ-2000 series reaches its limit? What will happen when system C-AJ-2999 is promulgated?
Answer: After C-AJ-2999 is issued, the next system number that UL will issue will have five digits, instead of four. The next system number will still start with 2, followed by four digits. The 2 at the beginning of the number series indicates nonmetallic pipe, conduit or tubing, and this will remain the same for the new numbering sequence as well. The next system numbers will be C-AJ-21001, C-AJ-21002, C-AJ-21003, etc.

Question: Does this affect existing system numbers?
Answer: No, UL is not changing any existing system numbers because the existing system numbers are referenced in many locations, such as customer websites, literature and other materials. Going forward, when any series runs out of system numbers, UL will expand the series numbering from four to five digits for new systems and keep the leading digit the same so that searching for a system in Product iQ will remain consistent with current practices and the type of penetrant, size of joint, or other information indicated by this number can still be recognized and identified.

Question: When will this take place?
Answer: UL has already completed the technology updates to support both the existing four digit sequence and the enhanced five digit sequence so that any searches in Product iQ will continue to work properly. At this time the C-AJ-2000 series of Through-Penetration Firestop Systems and the HW-D-0000 series of Joint Systems are the only two series that are nearing their end of available system numbers, so changes will take effect for them in the near future. Other applicable numbering systems will be altered as needed in the future.


Click the links below to access more information about the numbering systems.