The US model: the assembly is tested, not the coating
In the US, fire resistance is demonstrated by testing a specific assembly — a column, beam, floor or wall — together with all its components, including the fire protection. The result is published by the testing and certification organisation as a listing with a design number. Rather than “selecting a group”, the designer chooses a suitable tested design and follows its description. In Central Asia, US standards are in demand mainly on oil, gas and chemical projects, where client specifications often require testing to UL 1709.
Building codes and NFPA
Required fire resistance ratings in the US are set by model codes, which states and municipalities adopt in their own editions:
- International Building Code (IBC) — defines construction types and the required fire resistance ratings of building elements; the methods for establishing a rating (testing, calculation, prescriptive solutions) are set out in the chapter on fire-resistance-rated construction (Section 703).
- NFPA 5000 (Building Construction and Safety Code) and NFPA 101 (Life Safety Code) — alternative and complementary NFPA codes.
- In the oil and gas industry, fire protection requirements are usually set by industry recommended practices and client specifications that refer to hydrocarbon test methods.
In US practice, fire resistance ratings are expressed in hours: 1 h, 1½ h, 2 h, 3 h, 4 h.
Standard fire: UL 263 and ASTM E119
ASTM E119 “Standard Test Methods for Fire Tests of Building Construction and Materials” and UL 263 “Fire Tests of Building Construction and Materials” are technically equivalent fire resistance test methods using the standard exposure. ASTM revises E119 regularly, so documents cite different edition years; always check the current edition on the ASTM website.
Key features:
- The ASTM E119 standard time–temperature curve is close to ISO 834 but is defined by a table of points rather than a formula; in the first few minutes it differs somewhat from the European curve.
- Assemblies are tested under load; for beams and floors, a distinction is made between restrained and unrestrained ratings.
- For steel columns tested without load, the standard applies a temperature criterion: the average steel temperature at any of the measuring sections must not exceed 538 °C (1000 °F), and the temperature at any single point must not exceed 649 °C (1200 °F).
- For walls and partitions, a hose stream test (a jet of water from a fire hose nozzle) may be required after the fire exposure.
- For separating elements, the temperature rise on the unexposed surface is limited.
Hydrocarbon fire: UL 1709 and ASTM E1529
UL 1709 “Rapid Rise Fire Tests of Protection Materials for Structural Steel” is one of the most widely used test standards for fire protection of steel in the oil and gas industry. It was first published in 1991; the current (sixth) edition was issued in 2022.
- “Rapid rise” exposure: the temperature at the specimen reaches 1093 °C (2000 °F) in about 5 minutes and is then maintained. At 5 minutes this is roughly 150 °C above the European hydrocarbon curve.
- The test assesses a steel temperature limit rather than load-bearing capacity: the criterion is an average steel temperature of 538 °C (1000 °F).
- UL 2431 “Durability of Fire Resistive Coatings and Materials” is the UL standard for assessing the durability of fire protection coatings and materials: specimens are first conditioned in adverse environments (wetting, freezing and drying cycles, salt spray, industrial atmosphere, ultraviolet light, etc.) and then fire tested. According to UL Solutions, UL 1709 requires this evaluation for all fire protection systems certified to it, and the system must meet Category I-A (Outdoor, Heavy Industrial); compliance is shown in the system’s listing in the UL Product iQ directory.
ASTM E1529 “Standard Test Methods for Determining Effects of Large Hydrocarbon Pool Fires on Structural Members and Assemblies” (current edition E1529-22) simulates the total engulfment of a member in the flames of a large hydrocarbon pool fire. The method specifies both the source temperature and the heat flux to the specimen, and includes procedures for loaded and unloaded columns and beams, as well as for fire walls. The standard itself notes that it does not give complete information on structural behaviour during the first 5 minutes, because the specified ramp-up time is longer than in a real fire.
UL listings and design numbers
Test results to UL 263 are published in the UL Solutions certification directory (Product iQ) under category BXUV — Fire-resistance Ratings, ANSI/UL 263 (BXUV7 for Canada). Each design has an alphanumeric number in which the letter indicates the type:
| Prefix | Type of assembly |
|---|---|
| X, Y | Columns |
| N | Beams within floor assemblies |
| D | Floors: concrete on profiled steel decking, supported on beams |
| U, V | Walls and partitions |
The design specifies section sizes and types, the type and thickness of fire protection, the fixing method and permitted substitutions. The rating is valid only if all the conditions of the design are met. The designer references the design number, and the inspector checks that the installed solution complies with it.
Similar listings for hydrocarbon tests to UL 1709 are published in the corresponding directory categories. In practice, fire protection documentation for oil and gas facilities cites a UL 1709 certificate or listing with thickness tables for different sections and durations (e.g. 60, 90, 120 minutes).
Penetration seals and cables: UL 1479 and ASTM E814
The fire resistance of seals where services (pipes, cables, cable trays, ducts) pass through walls and floors is tested to UL 1479 “Fire Tests of Penetration Firestops” and ASTM E814 “Standard Test Method for Fire Tests of Penetration Firestop Systems”. The specimen is subjected to the standard fire exposure and a hose stream test.
| Rating | Meaning |
|---|---|
| F | The seal remains in the opening and prevents the passage of flame, with no flaming on the unexposed side; it withstands the hose stream |
| T | In addition, the temperature rise on the unexposed side is limited |
| L | Air leakage (based on the results of an air leakage test) |
| W | Watertightness in a water leakage test |
Firestop systems are published in the directory with numbers of the form “wall/floor type — penetrant type — number”. As with assemblies, the rating applies only to the tested combination of materials and sizes.
Comparison of the key US methods
| Standard | Purpose | Exposure | Result |
|---|---|---|---|
| UL 263 / ASTM E119 | Columns, beams, floors and walls of buildings | Standard (cellulosic) | Assembly rating in hours |
| UL 1709 | Fire protection of steel at facilities with a hydrocarbon fire risk | Rapid rise, 1093 °C in about 5 min | Time to an average steel temperature of 538 °C |
| ASTM E1529 | Structural members and walls exposed to a hydrocarbon pool fire | Specified temperature and heat flux | Time until the criteria are reached |
| UL 1479 / ASTM E814 | Service penetrations | Standard + hose stream | F, T, L, W ratings |
Applicability in Uzbekistan
US listings and test reports do not replace the requirements of ShNK (Uzbekistan’s Urban Planning Norms and Rules), but they are often used as evidence of material performance, especially at oil, gas and chemical facilities. When using them, bear in mind that an hourly rating applies to a specific assembly, and that the 538 °C criterion differs from the 500 °C adopted in GOST R 53295. Thickness tables in US documents are tied to section massivity expressed in US units (W/D, A/P), so conversion to GOST section sizes must be carried out carefully and documented.