What is UL9?
UL9 is the Underwriters Laboratories standard for fire tests of window assemblies. It evaluates the ability of window systems, including glazing, to resist the passage of flame and hot gases during a standard fire exposure. For fire-rated glazing in the US market, UL9 is one of the primary test standards referenced by the International Building Code (IBC) and NFPA standards.
UL9 is closely related to UL10B (fire tests of door assemblies) and UL10C (positive pressure fire tests of door assemblies). Together, these standards form the backbone of fire-rated opening protective testing in North America.
UL9 vs NFPA 80 vs NFPA 257
UL9
Tests window assemblies for fire resistance. Evaluates the entire assembly including glazing, frame and seals. Results in hourly ratings (20 min, 45 min, 60 min, 90 min, 180 min).
NFPA 80
The Standard for Fire Doors and Other Opening Protectives. Governs installation, inspection, testing and maintenance of fire-rated openings. References UL9, UL10B and UL10C for glazing in fire doors.
NFPA 257
Tests fire test of window assemblies using an alternative methodology. Some jurisdictions accept NFPA 257 in lieu of UL9. Both standards measure integrity under standard fire conditions.
IBC Requirements for Fire-Rated Glazing
The International Building Code (IBC) specifies where fire-rated glazing is required and the minimum ratings. Key provisions include:
- IBC 716.1: Opening protectives in fire-rated walls and partitions must have the same fire rating as the wall itself.
- IBC 716.3: Fire-rated glazing in doors must be tested as part of the door assembly (UL10B or UL10C).
- IBC 716.5: Fire-rated glazing in sidelites and transoms adjacent to fire doors must meet UL9 or NFPA 257.
- IBC 716.6: Fire window assemblies in exterior walls must meet UL9 with the rating specified for the wall.
- IBC 716.7: Maximum allowable areas of fire-rated glazing vary by building type, occupancy and fire separation distance.
UL9 Hourly Ratings Explained
UL9 assigns hourly ratings based on the duration the assembly resists flame passage. Unlike European E/EI classifications, US ratings are expressed in minutes or hours:
| Rating | Duration | Typical Application |
|---|---|---|
| 20 min | 20 minutes | Smoke barrier windows, low-risk compartments |
| 45 min | 45 minutes | Fire door vision panels, residential corridors |
| 60 min (1 hr) | 60 minutes | Commercial fire walls, office partitions |
| 90 min (1.5 hr) | 90 minutes | High-rise compartment walls, stairwells |
| 180 min (3 hr) | 180 minutes | Industrial fire walls, hazardous areas |
Fire Door Glass and Vision Panels
Fire-rated glazing in doors is governed by NFPA 80 and tested under UL10B (neutral pressure) or UL10C (positive pressure). Key requirements:
- Glass must be labeled with the fire rating and the certifying agency (UL, Intertek, etc.)
- Maximum glass size is limited by the door manufacturer's listing. Typical limits: 100 sq in for 20 min, 1296 sq in for 45-90 min.
- Glass type must match the tested configuration. Wired glass, ceramic glass and special tempered glass each have different listings.
- Frames, glazing beads and intumescent seals must be part of the tested assembly.
- Sidelites and transoms adjacent to fire doors require separate UL9 testing unless specifically included in the door assembly listing.
Sidelite and Transom Requirements
Glazing in sidelites (adjacent to doors) and transoms (above doors) has specific requirements under IBC and NFPA:
- Sidelites within 48 inches of a fire door must have the same fire rating as the door (typically 45 min or 60 min).
- Transoms above fire doors must be tested as part of the overall opening protective or separately under UL9.
- Maximum vision area in sidelites is typically limited to 25% of the wall area between doors.
- Fire-rated glazing in sidelites must carry a permanent label visible after installation.
Temperature Rise vs Integrity Ratings
In the US system, fire-rated glazing can have two types of ratings:
- Integrity only: Prevents flame passage but does not limit temperature rise. Marked with the hourly rating only (e.g., "45 min").
- Temperature rise + Integrity: Limits temperature rise on the non-fire side to 450 degrees F above ambient at 30 minutes. Marked with "XXX T" (e.g., "45 min T" or "60 min T").
Temperature rise ratings are required for glazing in exit enclosures (stairwells and exit passageways) under IBC 716.5.3. This is roughly equivalent to the European EI classification.
UL9 Fire Glass Specifications Quick Reference
| Application | Typical Rating | Max Size | PyroSpec Product | Test Standard |
|---|---|---|---|---|
| Fire door vision panel | 20-90 min | 1296 sq in | PS-FR Door Vision | UL10B / UL10C |
| Sidelite (adjacent to fire door) | 45-60 min | Per IBC limits | PS-FR Sidelite | UL9 / NFPA 257 |
| Transom (above fire door) | 45-60 min | Per IBC limits | PS-FR Transom | UL9 / NFPA 257 |
| Interior fire window | 45-90 min | Per IBC Table 716.6 | PS-FR Window | UL9 |
| Exterior fire window | 60-180 min | Per IBC Table 716.6 | PS-FR Curtain | UL9 / NFPA 257 |
| Smoke barrier glazing | 20 min | Unlimited (smoke only) | PS-Smoke Guard | UL9 |
Labeling and Marking Requirements
All fire-rated glazing in the US must carry a permanent label visible after installation. The label includes:
- Certifying agency (UL, Intertek/Warnock Hersey, etc.)
- Fire rating in minutes or hours
- Whether temperature rise rated ("T" designation)
- Manufacturer name or identifier
- Product traceability information
Labels must be applied by the manufacturer or fabricator and cannot be added in the field. Missing or illegible labels are a common reason for failed inspections.
Fire Marshal and AHJ Inspection
The Authority Having Jurisdiction (AHJ), typically the fire marshal or building official, inspects fire-rated glazing for:
- Correct rating for the location (matches wall/door rating)
- Proper labeling (permanent, legible, correct agency)
- Installation matches the tested configuration
- No field modifications (cutting, drilling, notching)
- Frame and hardware compatibility
- Intumescent seals properly installed
PyroSpec supplies installation certificates and compliance checklists to support AHJ inspections.
Why US Projects Choose PyroSpec
UL-Recognised Test Reports
Fire test reports from laboratories recognised by UL and Intertek, accepted by AHJs across all 50 states.
NFPA 80 Compliance
Full documentation supporting NFPA 80 inspection requirements, including labels, installation instructions and maintenance guides.
IBC Code Compliance
Products designed to meet current IBC provisions for fire-rated openings, with code compliance letters for plan review.
Direct Export to US
Experience shipping fire-rated glazing to US projects with proper customs documentation, HS codes and freight coordination.
Frequently Asked Questions
What is the difference between UL9 and UL10B?
UL9 tests window assemblies (including sidelites and transoms). UL10B tests door assemblies. If you need glazing in a fire door, it must be tested under UL10B or UL10C as part of the door assembly. If you need glazing in a window or sidelite, UL9 applies.
Does UL9 require temperature rise testing?
UL9 itself tests integrity only. However, IBC 716.5.3 requires temperature rise ratings (450 degrees F max at 30 min) for glazing in exit enclosures. This is typically denoted with a "T" after the rating (e.g., "60 min T").
Can I use CE-marked fire glass in the US?
CE marking is not recognised in the US. Products must have UL, Intertek or other ANSI-accredited testing. However, the underlying fire test data (to EN 1363) can sometimes be used as supporting evidence if the product is also tested to UL9.
What size fire-rated glass can I put in a fire door?
Maximum sizes are determined by the door manufacturer's UL listing. Typical limits: 100 sq in for 20 min wired glass, 1296 sq in for 45-90 min ceramic or special tempered glass. Always check the specific door listing.
Does PyroSpec supply labeled fire-rated glazing for the US market?
Yes. PyroSpec supplies fire-rated glazing systems with UL-recognised test reports and permanent labels. We coordinate with US fabricators and door manufacturers for proper labeling and listing compliance.
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