UL 10B and UL 10C are not interchangeable shorthand for “any gasket fits a fire door.” The UL guide associates category GVWZ with fire-door gasketing evaluated to UL 10B and GVYI with positive-pressure-tested edge sealing under UL 10C. Those are category descriptions, not approvals for a particular SKU and door.
Manufacturer documents and safe interpretation
- UL Appendix A identifies category GVWZ with gasketing materials for fire doors investigated using UL 10B. Publisher document — PDF printed p22 / zero-index p21 > Appendix A category code table GVWZ.
- The same table identifies GVYI as positive-pressure-tested fire-door gasketing and edge-sealing material under UL 10C. Publisher document — PDF printed p22 / zero-index p21 > Appendix A category code table GVYI.
- The UL gasket/edge-seal discussion differentiates the limited purpose of GVWZ materials from positive-pressure-tested GVYI materials. Publisher document — PDF printed p11 / zero-index p10 > Gasketing and edge seal materials.
- UL further treats S-marked smoke/draft door assemblies and Category H gasketing as an additional UL 1784 evidence question. Publisher document — HTML Leakage rated Door Assemblies > S-rated door assemblies.
How to make the distinction
Read a claim in three layers
- Category name: Is the document about GVWZ (UL 10B), GVYI (UL 10C) or something else? Preserve the exact code from the issuer record.
- Product certification: Does the record identify the precise manufacturer, product and certification conditions? An abbreviation on a resale listing is insufficient.
- Assembly application: Does the installed door's manual require specific components, locations or material categories? Verify with the complete assembly record and reviewer.
| If you see | Treat it as | Do not call it |
|---|---|---|
| GVWZ / UL 10B in a UL category table | A fire-door gasket evaluation category | Smoke-control assembly approval |
| GVYI / UL 10C in the table | Positive-pressure fire-door gasket/edge-seal category | Automatic authorization for every existing door |
| S mark / Category H reference elsewhere | Additional smoke/draft-specific question | A synonym for either of the two rows above |
Reader checklist: identification and safe handoff
Copy the category code, precise listing identifier and document edition into a review sheet; then record what is actually written on the door label. Ask the fire-door professional or authority to compare the named product and installed assembly. If only a generic “UL-rated” marketplace statement is available, mark certification unresolved and stop selection.
What the evidence does—and does not—settle
Supported: using category codes to ask better questions. Not supported: deriving legal acceptability, smoke rating, service part fit or current certification from a historical appendix table alone.